YouTube has a lot of things going on, with new user-generated video genres arising all the time. A good example are Supercuts, remixed videos created from clips from TV shows, movies, video games or commercials. They tribute videos could be likened to animated collages.
People cut out the stuff they like best, and arrange them in ways meaningful to them. Some play with the dialog, while others dupe over it with music or other narration.
It's a great way for the creators of the original media to see what their viewers find most appealing, and gives them clues on how to make their content even more relevant to their viewers.
The best one I've found is the one feature above, a montage of the best viral videos on the web!
Check out Weezer's spoofed viral video supercut: