In my opinion, that's essentially a ranking problem, not a conceptual block. There's no doubt a wide-open field of "how to get recommendations right" once thin

In my opinion, that's essentially a ranking problem, not a conceptual block. There's no doubt a wide-open field of "how to get recommendations right" once things have moved over in that direction. One of the key ways of doing that will be figuring out how to weigh different sorts of interactions -- it won't just be so-and-so-likes-this, but also taking into account profile views, messages sent and so on.