I have a Twitter account for my business, and think its worthwhile. I've also ooohed and aaahed over the things other people are doing with their Twitter's. Still, I have regarded having a personal Twitter as a waste, and indicative of being a waste (of amino acids). But, I'm slowly changing my mind, and as such have stuck a toe in the water.
Changing my mind have been artists I like, such as Corb Lund and Amanda Palmer, various writing movements like Nanoism, writers like Steve Pressfield, and the recent happenings in Iran where Twitter was put to such good effect.
So, I now have a Twitter. At present, I'm enjoying it and delighted that things I see there already make my world feel more right and well adjusted (which I did not expect). Like the Kindle thing, it may stay, or it may go the way of the Sardinian Dhole.
I think I'll be using it to follow people primarily for now, but I expect I'll be tossing up some original 140 character prose from time to time as well.