Agreed. User base in a internet facing app means something when users visit the site to interact. Twitter is such an open platform for communication (like email, sms, and hell, even the web) that monetizing it as a service seems impossible.

I would venture to guess that based on revenue Tweetie is more valuable that Twitter itself. Myspace, Youtube, Facebook, they all have pageviews.

Twitter was founded as an SMS service and won't ever be able to fully monetize the platform unless they close the API (which they won't).