Like lots of people, it took a while for the penny to drop in my head about Twitter. At first I didn't really get the point.  I do now.  A colleague in the US, Bernie Borges has posted an article on his site titled, "Top reasons I follow Back On Twitter.  Incidentally, it's worth doing. 

Take a look at his article at http://www.findandconvert.com/blog/2010/top-reasons-i-follow-back-on-twitter/