Great blog posting about this subject:
Per Facebook’s own Social Ad Platform, they now have 71.9 million US users as of 7/4/09. That is a 70.8% increase since 1/4/09. The most significant increases come from from the 55+ crowd. Losers are at the younger end with 16.5% less high school users, and 21.7% less college users. What does all this mean? We constantly hear about the amazing stats on Facebook and how great an opportunity they are for entrepreneurs to Fortune 500 businesses.