devising a classification matrix for uses of Twitter

As some people might be aware I've got my teeth into Twitter at the moment. As part of this, I'm wondering if I could devise a robust-ish classification index for the different types of Tweets. The intention is to use this as a way of introducing people to how twitter is being used, and also map against this various types of learning activities.

The process is relatively straight forward. I'll work up an index based on my observations, then sample a proportion of people that I follow on twitter to see if the index actually works, i.e., captures to an acceptable level the type of tweets. 

The starting point is developing the index, and this is where I need your help :-) Below is the first iteration. I was wondering if people would like to leave comments in terms of am I missing uses, clearer explanations etc., Alternatively, this has already been done at ... so don't re-invent the wheel !

Classifying tweets- iteration # 1

• Social awareness - these are mostly updates to keep people connected. These are divided into personal and/or work related. The way that they are phrased doesn't invoke a response.

• direct 1-2-1 communications with other people

• Team awareness - these were directed to a sub group of followers who are members of the elearning team at the University

• Personal - these where placeholders of thoughts during conferences and workshops. This is micro-blogging in that the audience for these was me.

• Questions - this was a "scatter gun" approach of asking questions to my followers and seeing if anyone will responds. So the difference between this type and the social awareness is that they encouarge a response.