There was some controversy last August when FXX ran classic Simpsons episodes cropped at 16:9 for modern HDTVs, instead of their original 4:3 "Academy" format. (The show switched to HD and 16:9 in 2009, but this only applies to the last five-and-a-half seasons.) Apart from not reflecting the original style or composition of the older shows, this reformatting ruined a number of visual jokes, chopping off the tops and bottoms of the frame to create a fake "widescreen" effect.
But it's all good now: Fans can stream the first seven seasons in their original aspect ratio from FXX's website. It's not entirely clear when or if Seasons Eight through Twenty will get the 4:3 option, but it's probably a safe bet that the majority of Simpsons fans passionate enough to complain about the cropping probably don't want to watch anything made after 1996 anyway. (Caveat: It looks like mobile users will have to wait a little longer.)
The last few months have seen some controversy arising over aspect ratios in older television shows. FX notoriously ran "remastered" episodes of Buffy in widescreen that revealed technicians and equipment, and there's some question as to whether or not the first five seasons of The X-Files should be shown in the 16:9 format. Composition is as integral a part of a movie or television show's identity as any other element — see David Simon's comments on HBO's planned HD conversion of The Wire. In a lot of cases, "upgrading" a show to widescreen in the belief that it improves the experience is just as misguided and media-illiterate as Ted Turner's plan to "fix" old black-and-white movies through colorization. When CBS Digital remastered Star Trek: The Next Generation for Blu-Ray, the producers were adamant about retaining the 4:3 aspect ratio, because that's the way it was intended to be seen. It's understandable that the studios would want to fill out the entire HDTV screen, and lots of '90s shows like Friends and Seinfeld have been "opened up" for the digital era. But there's some question as to whether that's always desirable.
The good news is that thanks to the Internet, fans are much more informed about these issues, and have a means of responding and even affecting change in a rapid fashion. Back in the dark days of VHS, it was very hard to explain to people why widescreen movies needed to have black bars at the top and bottom of the TV screen in order to accommodate the full image. Nowadays, it seems like consumers are more accepting of the "pillarbox" format in older movies and TV programming — and are more than capable of giving the studios an earful if they mess up their favorite shows and films.