Facebook growth has fallen dramatically, signaling that nearly everyone who is likely to have a Facebook account has one. The U.S., Canada, Russia, Britain, Norway, and Russia all posted lower numbers of new users and higher numbers of closed accounts. Like the blogging bubble of a few years ago, a lot of people have tried Facebook and have found they don't have much use for it. That's not meant as a criticism--I use Facebook for family stuff and like it--but it is a reality of online services going all the way back to the early growth of email. No online service can sustain double digit growth forever, and AOL learned this the hard way. What will be interesting to watch is if Facebook can institute internal cost and staff controls that keep the company in the black as their subscriber base stabilizes.