financial models by headcount

I've seen head-count burn-rates calculated at a couple of places, but it's not the norm.

http://blog.guykawasaki.com/2007/10/financial-model.html

Scroll down to the bottom, in part II: lessons.  The number 1 take-away was Focus on headcount.  Granted, that won't work for all business models, but it is interesting how accurate it turns out to be.