I like it. I think simplistic interfaces are the way to go for collaborative/social apps.

The downside of course is that it's dead easy to clone these simple apps (like Twitter, TinyURL, etc.), which means the barrier to entry for your competition is quite low. This effect has been recently amplified with the boom in quality frameworks and dirt cheap infrastructure (EC2, App Engine).

The end result is that making a killer web app is not enough and you instead have to make sure you nail the social marketing of it and build up a large enough userbase that the brand/userbase becomes the real value.