Viacom demanded the immediate removal of all the fan videos, full-length episodes and whatnot of shows that it owns. YouTube complied. So then, all the uploaders of the banned material just moved to other websites, where their work is still proudly on display. Moral of the short story? Viacom are idiots.
Personally, fanvids, fanart and fanfics are all ways to express how much we enjoy Avatar and a way to increase whatever talents we may want to develop. There are some truly amazing artists on DA, some excellent writers on fanfiction.net and generally awesome...people who make fanvids. Yeah, I don't know what the name is for them. But still, Viacom shouldn't punish people by removing their creativity just because those people have used three minutes worth of material that, let's face it, viewers wouldn't be able to figure out the story from anyway. If anything, fanvids increase the shows popularity: I sent a fanvid with a great song on it to a friend, now he watches Avatar too. The Internet is a free place where people can express themselves in various different ways and with Viacom becoming the Hitler/Stalin/Mussolini (I have a history exam in a couple of weeks, give me a break ) of the worldwide web, more people will realize what's going on and start to fight back.