“I am whole heartedly for a tool to audit whether others are complying with your licensing terms.”
I was also thinking of something beyond this, as well. For example, people who buy music consistently might be given special treatment by artists, compared with people who consistently don’t pay. Or, whether or not there’s any payment involved, people who are good distributors on sharing networks are maybe more valuable to artists than leeches.
Similarly, someone who downloads your song and listens to it only once is maybe someone who needs more free stuff rather than being required to pay for what they have.