So this past week my alma mater had a flashmob at the all-campus picnic before classes started. I wasn't there, but through the wonders of Twitter, Facebook, and YouTube, I was able to see it. And as a result have spent the whole morning watching YouTube videos of flashmobs (specifically, the spontaneous bursting into song ones).
Fair warning: if any of my friends know of a flashmob that's looking for participants and doesn't tell me? We're no longer friends.