Its a cool idea, and definitely one that has crossed my mind a few times. I would guess you could build up common groupings of user preferences to try and provide group content filtering/rating? If not, would be fun to try
Agreed, moving towards collaborative filtering is a good idea. We have only a few users right now, so customized categories is mostly content based filtering and figuring out how to recombine the ranking signals for them. That often work fairly well to improve topics (sometimes drastically), but mixing in collaborative filtering seems like an exciting opportunity for improving.
Also hi, I'm Ben, and I worked on this.