Students in my classes use Facebook to share photos of trips, parties, their boyfriends/girlfriends, etc.
The advisors in our department, however, are alerting students to the fact that prospective employers use these sites to check up on job candidates.
So it may be that students will begin to be more circumspect about what they put on them. Or figure out sneakier ways to hide the incriminating stuff.
Meantime, keeping students off Facebook and instant messaging in the classroom (I teach in a computer lab) is a challenge.
I suspect that “teens” as they are now called have long done and said foolish things, some more than others. What has changed is that they now can advertise their thoughts and actions to anyone who wants to know for any reason, good or bad. I wonder if the novelty of self-revelation to strangers, perfect and imperfect, will soon lose its charm.