Facebook has hit 100 million active users. No formal press release has been issued, so you're going to have to believe the guy who built the site.
The news came straight from the source: Facebook founder Mark Zuckerberg and several of his fellow executives put it in their status messages on the social network, and platform manager Dave Morin broadcast it in his Twitter feed. At least one of them referred to the number being "active users," the statistic that Facebook prefers to use, rather than registered accounts overall.
While Facebook got its start at Harvard University in Cambridge, Mass. in 2004, most of this recent growth is coming from outside the U.S. Recently released statistics for July from traffic firm ComScore say that out of the approximately 145 million unique visitors coming to Facebook's domain, under 40 million of them were from its home country.