Twitter killer

After my last post about Twitter, I started wondering why someone hasn't come up with a Twitter killer yet. Twitter's infamous downtime and limitations such as 140 characters per message (understandable if you're using SMS, but not if you're Twittering from your laptop, as most of my friends do) scream for someone to come along with a better system. Twitter reminds me of Friendster in the early days of social networking. I wonder when the Myspace and Facebook of Twittering will come along and squash the pioneer.