I joined Facebook about a year ago, and I am amazed at how many of my friends from high school and college are using it, too. I'm in my early 30's, and my husband is in his late 30's - and pretty much everyone we know has "friended" us.
Before I signed up for an account, I was convinced that FB was "just for kids." And in some cases, it is. My husband's niece, for example, who is 19, sent out evites via FB to her wedding. (I must confess that this cracked me up - though she also sent out lovely, traditional hard copy invitations, too.) Though I can't see any of our contemporaries using Facebook for their wedding invitations, I DID just get an invite to my 15-year high school reunion.
Interestingly enough, I've also started using FB at work, to market some of our condominium properties. The channel came highly recommended from the EVP of Marketing at our condo broker partner, and though I will admit that I am still a teensy bit skeptical, I really do think that it will generate some significant traffic for the sites. Our biggest demographic is first-time home buyers, so it seems to be a natural fit.
Not surprisingly, FB has a boatload of metrics built into its reporting system, so advertisers can see exactly what they're paying for...and because we can set up the campaigns as pay-per-click, we literally have nothing to lose: no clicks, no cash outlay. We're hopefully launching the campaigns next week.