Facebook could use more older women, not to mention younger people in general. As the company pushes toward what is expected to be an IPO in 2010, it needs to shore up its user base in all demographics, if for no other reason than to diversify against a new social media platform that appeals to a specific community. So, even with the site pushing past 100 million monthly active users according to its advertising tool, with the addition of 5 million in December, there is work to be done if Facebook will make a successful entry into the public market.

Long derided by "serious folk" as a place for kids, Facebook's membership consists mostly of adults. Fifty-six percent of the user base is female, and 60% of users are 25 years of age or above. In fact, 20% of them are at least 45 years old. Some of the groups that are underrepresented are showing rapid growth. Men over 55 grew twice as fast as their female counterparts, though the younger generation moved onto Facebook most aggressively last year. Users age 26 to 34 showed the biggest overall increase in 2009, with 839,000 monthly active users. This represents a substantial shift from the trend earlier in the year, in which it was the later generation flocking to Facebook. Women over 55 didn't jump on the bandwagon as quickly as other groups.