There's another form of "favorites" that's maybe specific to audio / video, which is "playlisting."

In general, it's the ability to assemble different items into a new presentation. So, that can happen with text on wikis or via social bookmarking, etc. Maybe people do something like this on some photo sites.

But, specifically, with audio and video, there's an attractive creative form of participation when people can assemble a sequential collection of clips / tracks into a playlist or watch list. It's like creating a mixtape. And, YouTube invites people to do this with videos, for example.