I think what I got really wrong was the flexible nature of Twitter. A year later I find myself on "The Future and Your" podcast saying why "Twitter was better than Facebook"
Twitter has won me over because of its flexibility. Its core simplicity makes it the global market place for ideas. By using search terms (begun with # many times) or locating on people or places, including some great Web 3.0 mash-ups with Twitter, and the emergence of Foursquare has really turned me in to something of a Twitter evangelist and advocate.
Twitter shows that less can be more and simplicity can be strength. The content is out there, in micro pieces that can be assembled based on person, semantic content, or location. Who, what, where is there. You can look at Tweets over time so you have the ability to mine Twitter on Who, What, Where, and When. I can look at what some key people in a group are doing in North London about Sustainability.
What makes Twitter an killer app is the TinyURL and authentication link in. So I can join other Web 3.0 mash-ups with my Twitter account, and I can follow Twitter searches to new kinds of information.
Facebook is where you find, Twitter is where you meet. Twitter could easily be mashed up in to almost anything you want in a Social Network: a dating site, a political site, a blog, even a organisation tool.