Interesting. It would be good to know when these posses were so formed and actually referred to as a posse comitatus.

It's also interesting to read in jheem's commentary about the connection between count and companion--someone to break bread with. I would imagine there had been a divide between the earls and thanes--and those with whom they trusted enough to share the breaking of bread.

As a slight tangent, there is a moment in Poe's 'Tell-Tale Heart' in which Poe writes that men had been 'deputed' to investigate a cry heard in the night from the house in which the central persona of the tale had murdered the old man. That is the only instance I can recall in a story in which the verb 'to depute' had been chosen over the use of the noun 'deputies.' It is clear that a posse comitatus would be called out for more of a general public thread than an isolated murder as in the Poe story.