My kids use Twitter, so I have an account to see what is going on with them. We used to catch up on a phone call now and then, but the little things are not usually remembered. With Twitter/Facebook/Myspace it is more real-time keeping up - rather than the occasional phone calls. I don't tweet much because I am not as comfortable putting out my activiteis and feelings for everyone to see.

And Yes - you can reply to a tweet. You can also re-tweet. Probably other things too that I am not aware of...