Twitter Platform/API technical lead Raffi Krikorian posted an interesting map of what's going on behind your Twitter stream. As it turns out, there is quite a bit of data associated with not just you as a user, but also with every tweet that you post to the service.
Twitter status objects are continuing to expand (despite the 140 character limitation) as new functions such as geo-location and annotations make their way into the service.
One notable aspect is Twitter's focus on users' profile data including the number of status updates and where they sent the update from. As mobile adoption continues, it becomes clear Twitter could figure out a number of ways to target advertising and services on top of the basic messaging platform to expand monetization efforts.
The odd part about this map and the array data associated with each message is that it takes significantly more information to describe and contextualize each status update than the messages (Tweets) are capable of dealing with themselves.
And odds are the associated data will only get larger as more functions get built in, such as the ability to control message flow via hash tag or other mechanism.
Another way to see the structure of a Twitter message is through Apigee's recently launched API Console. Apigee is a free service that lets API developers test and debug APIs and provides the equivalent of Google Analytics for API traffic. An example of a Twitter status object as shown in the diagram above can be found here.
I do wonder a bit what the expansion of this data will do to third-party sites such as Foursquare that leverage Twitter information for aspects of their services and to what extent they will be able to deal with a continuously expanding database of user information. It definitely presents some new data management and reporting challenges in addition to a wealth of new potential new functionality.