Some of you may remember back to the days when only college students could use Facebook. It was a golden era, one of comparatively less ridiculous misspellings and inane 'groups' to join. Then the high school students joined, and the floodgates opened soon after that to admit everyone and their grandmother. And, as it turns out, their grandmother brought all her friends from the old folks home, and all of them sent out emails and phone calls and carrier pigeons to their seta-septa-and-octagenarian friends.

At least, that's one possible reason for why over 5 million people over 55 have joined Facebook in the last six months. The total number of seniors on the popular social site is now in excess of six million. Apparently their kids are too cool to hang out with them, both in real life and online. In the same period high school Facebook use has dropped 15%, and college Facebook use has dropped 20%.

This is very, very bad news for Facebook. While their numbers haven't started to flag, the ad demographic they provide is much less lucrative now. Seniors are substantially less attractive to advertisers than teens and young adults, which are both huge buying demographics. On the other hand, now they can land a lucrative contract with the Ensure people.

I'm not sure if there really is any way for Facebook to fix this. There could be a variety of reasons for change, including the amount of time they took putting in greater privacy options or the rapid spate of layout changes they've gone through. I think it's likely that they just got too old to keep the interest of their most coveted user group. It might be that Facebook has aged a little too much to keep the kids interested.