New users to Facebook (and probably some existing users, but not all of them yet) are getting a new search experience in Facebook starting Monday. The new interface for search makes it possible to see all public results from Facebook users (the Everyone filter), or just results from your friends. Or, as before, only Events, Groups, or Applications.
The Everyone filter is the key new feature. It lets Facebook users monitor the entire network for news and updates on big topics, the same way Twitter was consumed for information coming from Iran after the recent election.
Like Twitter Search, the Facebook search result page alerts you when new results come in that match your query, but it doesn't update the whole page until you ask. This is arguably the best way to keep people up to date without overwhelming them.
Facebook's 250 million-strong user base, and the demographic breadth of its audience, puts Twitter's geeky but growing audience to shame. However, Twitter and Facebook are not, strictly speaking, direct competitors. The standard social models for the sites are still quite different. In Twitter, by default, anyone can follow anyone else. In Facebook, however, people are accustomed to only reading updates from those people with whom they have established a two-way relationship. The new Everyone filter makes Facebook like Twitter in search, but it will take some time for people to learn to use Facebook the way they do Twitter, and it's not clear that the two models will mesh well on one social platform.