According to Inside Facebook - a Facebook watchdog of sorts - women ages 55 and over are signing up to the site at a blistering pace. This age group has grown by more than 175% since September 2008. In addition, the male segment over 55 grew by 137%, although the number of women stil outnumber men by a factor of two-to-one.

Over the past year or so, Facebook has seen an aging population - nearly half of Facebook's over 45 million users are over 26 years old. About 22% are 35 and older, while 8% are 45 and older, according to Marketing Charts. That may not sound much but, if my math is correct, that's about 3.6 million users in that age group. This presents a wonderful opportunity for those businesses targeting the 45+ crowd to get involved. And there are some groups inside Facebook that might be worth joining.

• Born in the 60's. Any of us out there? (20,145 members)
• People over 40 on FACEBOOK (6,353 members)
• Baby Boomers, over 50 (177 members)
• 50 and over and loving it! (125 members)
• I'm too old for Facebook, but I can't help it- it's like crack! (21,142 members)

You might notice that the 55+ crowd is under-represented here. In fact, the older Facebook crowd in general is not represented too well within Facebook Groups. So, it might be a good opportunity to create one and start recruiting.