As I mentioned here during the last boost in users (which was strangely initiated by multi-lingual blogspam), there's a sudden boost in sharing on my feed. I think this is what Hubski is all about - finding references to concepts and associating their user affiliation with it. In fact, there's a concept out there called ambient affiliation that I've studied quite extensively, and that I'm glad to see appear in the day-to-day.