It's probably worth noting that the main reason movies adopted widescreen format was because people were staying home from theaters to watch television, so movie studios decided they needed to offer something TV couldn't -- like a picture too wide to fit on a TV screen. Although of course the only reason TV had a 4:3 aspect ratio is because that was the original movie aspect ratio!
Of course, now history has repeated itself and modern TVs use the widescreen ratio, so movies have to do other things like go to IMAX and 3D, or that superhigh frame rate Peter Jackson's using for The Hobbit
. But now movie theaters have commercials before the films and modern screens are just really big digital TVs, more or less. So the lines keep blurring.