Two Facebook groups called “Million User” groups have grown from 1 user to 401,200 users in six days. Facebook is not going to re-install the old News Feed. The ads that he posts there generate between 6,000 and 7,000 clicks per day to “ClickBank”. Following the links makes money for the guy controlling the Facebook group. The next time you join a “million member group”, what you are really doing is helping these advertisers make it easier to spam you with their ads.”]
Source: http://garwarner.blogspot.com/2009/10/facebook-safety-million-member-facebook.html