Some recent work by Nancy Baym at the University of Kansas at Lawrence finds that common wisdom about people on the social web may be wrong. She finds that many people benefit from their on-line interaction in ways that help them in the real world. It is the exact opposite of socially isolating.
Her research compared groups of university students who were interacting either in person or in a chat room. Students who were either shy or anxious were a lot more likely to contribute and even to lead the group online than in person. And the other students developed better opinions of the shy and anxious ones. She also concludes that this online interaction could be practice for live interactions and therefore be helpful for the shy and anxious students when they are in real social situations. Rather than making them more introverted, it gave them social skill practice they could use in other situations. In a more general survey, she also found that time spent by students on Facebook was correlated with levels of empathy both online and off.
Is this what you would have guessed? My own research on the social web would have made me hesitant to jump to conclusions, but I am not sure I would have realized how helpful it was for shy students when they later get into live social situations to have practiced online.