I totally agree with your question regarding the use of Twitter. It seems a bit over the top to me, but I've heard it's growing in popularity among librarians and other student service groups. They're often using it to "broadcast" information to interested students via cellphone.
I'm using it with a group of 13-18 years olds we're taking to Chicago. Every 30-45 minutes they need to "tweet" us with their location. That way they get their freedom and we have some sense of where they are!
I've tried tweeting but Facebook status seems to fill the same function. A recent NITLE conference I attended tried to implement Twitter for networking but it never seemed to get off the ground to accomplish anything in a way better than a blog could. (For mobile blogging, I really like Vox)
I have uploaded my powerpoint presentation on Web Usability; due to agreements with the subject shown in the video clip I showed, I am unable to post the videos; sorry about that.