I wrote a thing about collaborative filtering for likes and dislikes! http://davidcelis.com/blog/2012/02/07/collaborative-filtering-with-likes-and-dislikes/
Collaborative Filtering with Likes and Dislikes
We’ve talked about some of the pitfalls of the five-star rating system and how a binary system based on likes and dislikes can be much better, but what does using this kind of rating system look like in practice? How can we take a user’s likes and dislikes and use them to generate helpful recommendations? The answer, as with the five-star system, is through collaborative filtering, but we can rely on a methodology better suited to a binary system!
I checked in at Addy's Sandwich Bar / Portland / OR