Read Lurking and Social Networks by Ton Zijlstra (Interdependent Thoughts)

Lurking, although the word seems to imply a negative connotation, has usefull aspects nonetheless. It is a way of determining rules of behaviour for new comers to a group.
The most obvious characteristic of a lurker is that he’s at the fringe of a group, listening and observing. Being at the fringe may seem like a bad place from the core, but in fact is a good position to build bridges to other groups, and be aware of other groups in the vicinity. In a face to face setting like a pub or a meeting of some kind, a lurker is visible, often shortly introduced after which the focus of attention shifts to the established group members again.
In on-line settings things are different. In some fora lurkers are encouraged to introduce themselves and then adviced to lurk, i.e. observe and learn for a while. But at all times there is no way of knowing how many lurkers are there that you are unaware of.
As lurkers are possible bridges to other groups, I as a blogger, would like to know:

How many lurkers I have, who read my blog but don’t comment or post.

Who they are
Serverlogs can give some clues, and I keep a close watch on them. Dave Winer’s RSS-tool also brings new info to light.