I think Twitter is a very interesting concept; here are some recent descriptive posts from many-2-many, by Ross Mayfield, and Liz Lawley. 

So I've joined Twitter.  I'll be a low frequency poster, I think. 

But the fact that there is a lovelylicious Mac app - twitterific - might put me over the easy distraction edge ...

For greater social value and worth, see this more interesting than I originally thought article in First Monday, by danah boyd, " ... Writing community into being on social network sites."  It captures a lot of the normal Sturm und Drang of social networks.