My dad is ESFJ and uses msn.com for news, because he doesn't know how to go anywhere else. And uses e-mail to keep in touch with friends and family. He doesn't care about the computer aside from that.
INTPs use the social networking sites a lot...? I don't really like to use that stuff. I'd rather have a topic to think about, or be doing research or something. There's a political board I post on, and an emulator gaming forum that I'm on the development team for. I still don't post on the public forums for the gaming forum that much since they discuss random crap.
On the other hand, I think I'm moving more and more towards S and J as I get older. My N and P scores keep going down and are almost at the middle.
One other problem I have, is that I'll think of a thread or a post I want to create, and I'll ponder it for awhile, but I don't feel like writing it out so it never gets posted.