Facebook crossed the quarter-billion user mark yesterday. That is 250,000,000 people. Head to the source for an interesting video which shows where people are signing up from over time.
"As of today, 250 million people are using Facebook to stay updated on what's happening around them and share with the people in their lives. The rapid pace of our growth is humbling and exciting for us, and it affirms that people everywhere are realizing the power of staying connected to everything they care about on Facebook."