Facebook just rolled out its take on Foursquare’s "check-in" feature, which lets you tell your friends — or the world, if you like — that you’ve just ambled into a specific venue. The twist? Unlike Foursquare, Facebook Places will let your Facebook pals go ahead and check you into a place, as well — cool if you're a freewheeling social butterfly, but troubling if you're at all protective of your privacy. (more)