There was a site called Nowmov (backed by Ashton Kutcher) that did something very similar, but took videos from twitter as ones to show. It's been shut down after a number of improvements, it is now called nowbox - a set top box and tv guide of youtube channels, apparently.

You could let people sign-in with youtube, grab their likes, favourites and subscriptions - analyze the tags of those videos and try and tailor videos around those. YT already has a recommendations tab so you'd be playing second fiddle to that.