Three years ago, my very funny colleague Jay Black penned a TV101 essay about the phenomenon of "channel drift." That's when a cable channel drifts away from either its original format or it keeps drifting from format to format. Usually you see channel drift when a channel keeps its name (like AMC) but not the format that gave it its name (classic movies).

But just because a channel drifts from its original raison d'être doesn't mean that it's making a horrible mistake. There are so many cable channels out there, along with online, mobile, and other viewing options, that a cable channel needs to change to survive. But they also need to keep the brand that they've built up over the decades.

So experimentation and change are pretty much a part of what most cable channels do. But some are doing it better than others. Here's a list of cable channels that have done a good job breaking away from their old formats, and channels that are fumbling the ball. I'll also mention shows that have survived the various changes, and if they're helping or hurting the current format.

GETTING IT RIGHT

AMC
Original format: Classic Movies
Current format: Kick-ass original dramas

AMC, along with FX, is the standard-bearer when it comes to cable reinvention. For years, the network showed classic movies without commercials, mostly the black and white titles that had been disappearing from broadcast TV's late shows. In between movies, Nick Clooney (yes, George's dad), Bob Dorian and other hosts would give behind-the-scenes tidbits and trivia about the movie just shown and the movie coming up.

It was a sleepy channel, but great for classic movie buffs. The advent of Turner Movie Classics, who grabbed the MGM library for themselves, led AMC to eventually change to a general movie channel, and in 2007, it debuted 'Mad Men,' its first original drama (it had tried comedy and reality in past years to not much success). A few dozen Emmys later, AMC has become a breeding ground for high-quality drama, from 'Breaking Bad' to 'The Walking Dead' to worthwhile experiments like 'Rubicon.'

FX
Original format: Reruns, theatrical movies and silly studio shows
Current format: Edgy original dramas and comedies

When FX debuted in the mid-'90s, it was known as "fx," in lower-case. It mostly showed reruns, but also had live studio shows where the hosts interacted with the audience, mainly by phone -- this was in the days when only nerds like me used e-mail and Mark Zuckerberg and the guys who created Twitter were still in grammar school.

It took a while for FX to find its way, spending a couple of years airing mostly reruns and theatrical movies, until it debuted 'The Shield' in 2002. The raw Shawn Ryan cop drama was so successful that FX became a home for drama, and eventually comedy, that was edgy and pushed the boundaries of what can be shown and said on basic cable. 'The Shield' is gone, but in its wake, a solid lineup of veteran shows remain, including 'Nip/Tuck,' 'Justified,' 'Sons of Anarchy,' 'It's Always Sunny in Philadelphia' and 'Louie.'

Bravo
Original format: Highbrow arts and entertainment fare
New format: Housewives, divas, and table flippers

Believe it or not, Bravo has been around since 1980, starting as a commercial-free channel that showed art house films, international titles, jazz concerts, and televised stage shows.

Thirty-one years and a number of owners later -- it's now owned by NBC Universal -- Bravo has transformed itself into a reality TV staple, starting with 'Queer Eye for the Straight Guy' in 2003. From there, Bravo's programming strategy has stayed remarkably consistent and cohesive, with reality phenomenons like 'Project Runway' (now on Lifetime), 'Flipping Out,' 'Kathy Griffin: My Life on the D-List,' 'Top Chef' and the 'Real Housewives' series attracting a strong viewership across the board (yes, straight men watch... don't let them tell you otherwise). It has such a strong identity that one of its executives, Andy Cohen, has become a star in his own right.

Hanging on for dear life: Somehow 'Inside the Actors Studio' has made the transition from Bravo's high art days to its current status as the top of the reality heap. While it doesn't fit in well with the channel's current slate, it's always fun to see James Lipton fawning over whatever recent star has decided to get a "grilling" from him.

TLC
Old format: Educational programming
New format: Little people, Gosselins, polygamists and loud cake makers

People should stop complaining already that the programming on TLC doesn't adhere to the channel's initials, which originally stood for "The Learning Channel." Even TLC's executives acknowledge that the "learning" part of TLC disappeared many years ago.

What people don't realize is that TLC started drifting away from its initial educational programming way back in the '90s, with shows like 'HomeTime' and crime shows like 'The New Detectives.' But when they debuted 'Trading Spaces' and their "Life Unscripted" slogan a decade ago, there was no more learning to be had. The channel has morphed from even that not-so-lofty perch to give viewers looks into the lives of unusual families, via shows like 'Cake Boss,' 'Little People, Big World,' 'Sister Wives,' 'Jon & Kate Plus 8,' '19 Kids and Counting' and 'Sarah Palin's Alaska.'

Hanging on for dear life: TLC still has a page for 'Trading Spaces' on their website, but it's not currently airing. Paige Davis even came back to save the former hit, but it may have finally met its maker.

GETTING IT WRONG

A&E
Old format: The "A" part of the name: highbrow arts programming
New format: The "E" part: depressing reality shows and lame dramas

It doesn't matter that A&E isn't doing its PBS-style highbrow programming anymore; that ship sailed a long time ago. It's not even that it does a lot of reality programming now. It's just that the channel seems to be a hodgepodge, programming-wise, not really carrying any sort of identity.

Does it want to examine the searing lives of people who are in desperate straits, like they do in 'Hoarders' and 'Intervention?' Do they want to show people with unusual jobs, like they do in 'Storage Wars?' Do they want to be celebrity-driven, like with 'Gene Simmons Family Jewels?' Or do they want to be a USA-like channel with accessible dramas like 'The Glades?' It's not that the shows aren't successful; it's that if you weren't a fan of any of them, you'd probably guess that they're on any other network than A&E, and that's a problem.

Hanging on for dear life: 'Biography' is still hanging around, despite the presence of the spin-off Bio channel, mainly because it can change and morph to match A&E's style at the time. For instance? A new 'Biography' of the man with the golden voice, Ted Williams, was just announced. You'd never see the show doing that in the days when it was doing the life stories of Tom Hanks and Johnny Carson.

Food Network
Old format: Chefs with personality
New format: Personalities with cooking skills

Don't get me wrong; I enjoy watching Guy Fieri talk about the "spicy train to Flavortown" as restaurant owners make vats of food on 'Diners, Drive-Ins and Dives.' And there's something about '5 Ingredient Fix' host Claire Robinson that makes me want to crack open a beer with her while watching a football game. But at some point, the Food Network decided to ditch most of the chefs who made the channel a household name and go with personalities who know how to cook.

Remember how obsessed you were with 'Emeril Live?' Those days are long gone. Once the network foisted Rachael Ray, whose meals weren't gourmet, but tasty and relatively easy to follow, on an unsuspecting public, the chefs were more or less history. Even the cooking shows you see in the mornings are now more personality driven than chef driven. No more Mario Batali showing us how to make fantastic Italian meals. Now it's Sandra Lee and her canned goods, Ray and her '30 Minute Meals' that really take 45, Paula Deen and her butter, the stoners on 'Ace of Cakes' and the one and only season of whoever won the previous year's 'Next Food Network Star.' They even gave Brian Boitano a cooking show, for heaven's sake.

Hanging on for dear life: 'Good Eats,' mainly because Alton Brown cannot be stopped. Also, the show is pretty damned entertaining. Bobby Flay seems to be the only true chef who still has a prominent place on the network (Tyler Florence is still around, but his profile isn't nearly as high), and if he didn't come up with 'Throwdown,' he might have disappeared, too.

VH1
Old format: Music videos for "old fogies" (i.e. over 25)
New format: I don't know... check with me next week

VH1 has had more formats than Joan Rivers has had Botox injections. First it was music videos, then it was pop culture skewering with shows like 'Pop-up Video.' Then it was wall-to-wall 'Behind the Music' documentaries. That gave way to talking-head shows like 'I Love the '80s' and 'Best Week Ever.' Next came "Celebreality" with shows like 'Celebrity Fit Club' and 'The Surreal Life.' Next was celebrity romance competition shows like 'Flavor of Love,' 'Rock of Love' and 'Tool Academy.' Now, the network is trying to get "real" with shows like 'Celebrity Rehab,' 'You're Cut Off!' and 'Tough Love.'

The formats have overlapped, but it does seem like VH1 reinvents itself every 18 months or so, doesn't it? It gets to the point where you won't be surprised to turn on VH1 some day and see Dustin Diamond as a Catholic priest.

TOO OLD TO JUDGE

MTV
Old format: Music videos by everyone from Duran Duran to Eminem.
New format: Whatever the kids are into these days

Let's face facts: If you're 30 and over, MTV is not programmed for you. MTV was there for you when you were between the ages of 11-29, in no matter what era you were that young. You either got into the Michael Jackson videos, stayed up late to watch 'Headbanger's Ball' or '120 Minutes,' watched your favorite band go 'Unplugged,' followed the seven strangers forced to live together on 'The Real World,' or watched Carson Daly talk over screaming teenagers on 'TRL.'

And, even though it's no longer "Music Television," the channel is still there for the tween-to-twenties set. There's no denying that their reality programming -- 'Jersey Shore,' 'Teen Mom,' 'Real Life' and '16 and Pregnant' -- have resonated with more people than some of their previous "reality" fare like 'The Hills,' which seemed to have a much more narrow audience. But MTV is still feeling their way in the scripted world, with 'Skins' being a critical and ratings failure and 'The Hard Times of RJ Berger' barely making a blip on the pop culture radar.

But, then again, I'm way too old to judge whether MTV is doing a good job or not. And I've been way too old for over a decade now.

Hanging on for dear life: The 'MTV Video Music Awards.' Why give awards for videos you never show?

Tell us: Which cable channels have done a good job reinventing themselves? Which ones have been a disaster?

Follow @joelkeller on Twitter and on Facebook.