According to a blogpost in Website Magazine

"News out of the UK last week shows that Facebook is taking over the top spot in the social networking scene. Nielsen/NetRatings states that Facebook received 6.5 million unique visitors in the month of August, 2007, compared to MySpace which drew in 6.4 million unique visitors. So the impending shift has finally taken place."

I think I have a facebook account. I remember logging in and going, "um OK…"