Facial recognition technology is already ubiquitous; I'm more worried about their messaging system!
Even the iPhone is going to be doing it with iOS 5.0. I'm not so much worried about this as the "work" Facebook has been doing integrating online and offline IM. For more than a week now I have messages in my Facebook Inbox from blocked users (some of them extremely abusive). I logged a bug report and got a boilerplate response asking for a "screenshot" despite my succinct initial bug description of "Inbox Bugs: Messages from blocked users appear in my Inbox!".
I value my privacy and spend a significant amount of time reducing my Google footprint (a la Facebook, LinedIn etc.) so I find it infuriating that Internet giants like Facebook see my privacy as something of tradable commodity...