Interesting article. I especially liked this:
Indeed, for now, Twitter appears to be winning the microblogging arms race. The service boasted an estimated 1.2 million unique visitors in May alone, and may be valued in the eye-popping neighborhood of $100 million. This all suggests that an instant 140-character “tweet” meets some communications needs better than a fleshed out blog post. (In April an American journalism student was arrested in Egypt for photographing a demonstration, his tweets alerted friends to what had happened—and ultimately got him sprung.)
I better start tweeting more!