I totally agree with the Dad comment here. Both my Mother and Father are hugely into Facebook, but don't understand twitter. They have both signed up for accounts, but haven't really used them, because they don't get it.

To be honest, I also didn't really understand twitter until I had to sign up for it to promote a talk I was giving at a conference. Then after playing around with it a bit, I found some interesting people I ended up following. Before that though I didn't really see the appeal. And this is coming from a tech and news junkie.