[Kolya]

as a guess, i would think the short-term churn has increased.

most heavy users of fb that i know are people that signed up a long time ago. it was an important part of their social life and most still use the site.

but recently, i've had a few more (older, less tech-savvy) friends on fb. they 'got around' to joining fb eventually. but because it wasn't as important to their social life to join, and they only bothered doing so after knowing about fb for a few years, they are more likely to drift away.

i don't know if that's true, but it doesn't sound too unreasonable.