When my sons mention to their friends that their mother is on Facebook, the first reaction of the friend is "oooh, that's cool". My sons give them a withering stare and say "Think about it. Would you want *your* mom on Facebook?" A slightly more dubious expression crosses the friend's face. And my sons smile and say, "Exactly..."
My sons will not "friend" me on Facebook, but they do connect with cousins (same generation cousins) on Facebook. We can all be on Facebook at the same time, but some relationships will be held at more of a distance in the environment than they would be in the physical world.
As a parent of a college student and a grad student, if they are any indication, they logged on as much during the summer as during the school year. It was how the grad student gathered information about what to expect in a completely different state and it was how the undergraduate kept up with his friends while away from home on a summer job. Facebook is most certainly a communication platform for that generation. If they were going to adopt an application over the past four to six weeks, they already added it to their profiles.