I've been playing around with Twitter and I like it, although I don't see myself using it as a social networking tool. What I like about it is it provides the ability to broadcast a message or announcement out to a wide audience. I've set up several different Twitter accounts and use them primarily as a means to post regular announcements to several websites I own. With Twitter, you can copy some HTML code and use this code to place a widget (is that the right term?) on a website to display messages. For instance, I set up Twitter accounts that I use with my 2 course websites. Now I can post updated announcements to these websites without having to modify and republish these websites every time. This is quite a time saver for me.

One of the classes I teach is at 7:30 in the morning and I am always concerned about running into an accident and being late to class and having no way to let my students know what is going on. With Twitter, I can now send a text message (or use Jott to send a verbal message) to my class and that announcement is posted to my course website within seconds.

I signed up for LinkedIn recently and made the same observation you did about classmates.com. The only reason I signed up for it was because I found an old friend there who I had lost contact with and wanted to regain contact with them. LinkedIn may be useful for some, but I thought it somewhat gimmicky and so I don't see myself doing much with it.

I haven't tried out Facebook, but that one sounds like a big time waster for me. I think I'd spend way too much time there....