There's a new service (in beta, of course) called Stellar that tries to make the favorites useful. It aggregates your favorites from Twitter, YouTube and Flickr. You follow people to see what they find funny or interesting and if you happen to favorite their favorites they're gonna get updated as your favorites back to their originating services.
I've found it a pretty good way to find interesting things to read and watch for those rare moments you need to kill some time. It might be that I'm following the right people and not too many of them, who knows how useful you'll find it. If you wanna try it out I happen to have two invites. Just comment on this post with your email address and I'll send an invite your way.