There's a lot to dislike about the Facebook user experience. The groups capabilities are pretty anemic, for example. And don't even get me started about making me go to a web page to respond to a private message. But I am finding some clever aspects that are worth emulating too. In particular, there is some subtle and clever work around subscription management. For example, if I comment on a photograph that somebody has posted, I am automatically subscribed to the comment stream for that photo. I have entered the conversation, and the system infers that I want to be kept abreast of it. There is nothing explicit in the user interface for this. I never had to click on "subscribe to comments" anywhere. The system figures out what I want from the actions I take.I suppose the danger of this approach is that the system will infer incorrectly and I will have no way to fix it as an end user, but so far that has not happened to me yet. I'm guessing this is because Facebook sets a fairly well-defined social context and that its designers can therefore make pretty good guesses about what people will want to have happen within that context. This sort of inferential system response is worth further thought, particularly in areas such as subscriptions and permissions, where explicit management by the users can become overwhelming very quickly.
Another thing I like is the "see more of" or "see less of" type features in the status updates. Sometimes I get friend requests from people I don't know and have never heard of. Because I am now a quasi-public figure (aren't well all?), I tend to accept these requests. But while I don't mind these strangers listening in on the public stream of my daily life (even if I don't quite understand why they would find it interesting), I don't necessarily want to know what they are doing in their daily lives. So I appreciate having the ability, when a status update from a person I don't know appears on my screen, to select the option to "see less about" that person in the future. Likewise, if I really like videos, I can choose to see more posted videos in the future. These features works well, in part, because the updates posted in Facebook are mostly casual and non-essential news items. It's hard to see how a "see fewer homework assignments" would be such a good idea in an LMS interface, for example. But the general idea of adding accessible and coarse-grained (and therefore intuitive) controls (not "show me 30% of this person's updates" but "show me less about this person") is also an interesting one that is worth exploring further.