What do I mean by "all kinds of data"? First, music. Ever seen a music video on YouTube that isn't really a music video, but simply a song with some pictures slapped on it just to kill the boredom? There are plenty of services for sharing audio files out there, but kids are using YouTube because they're used to it, because it's simple, and because all their friends are using it. AP has an interesting article on this topic.
It doesn't stop at music. You can find song lyrics (karaoke style) or even chords embedded in some videos; some users are sharing photos simply by stringing them into a video with music, etc. Video is definitely not the best vehicle for sharing all these types of data, but I see more and more users doing it; for them, it obviously works better than other available options.
Now, I'm not really sure if expanding focus to other types of data is the best course or even a good idea for YouTube. But I see untapped potential here; users are obviously already using these features - although they're not quite there - so why not provide them? Of course, the folks at YouTube would have to be extra careful not to overly complicate the service and/or confuse their users. But if they pulled it off well, it might turn out to be a very smart move.