I've been thinking this too: Twitter = YouTube. The argument: YouTube is now the second-most-popular search engine and Twitter Search (as we've previously mentioned) has immense potential to become the next big thing in search. Small prediction: Twitter hasn't released any new features in a long time, but the next thing we'll see is a fancy new search feature (geo stuff? retweet/favorite filters? something....) that includes a revenue model. (More info: Borthwick had similar musings about Twitter Search a couple weeks ago.) Update: more context from Honan in the comments.