Re: I think it's a reasonable idea.
I don't think it's reasonable. The number of people running software (installed by them or part of an application or OS) is ever increasing. People using random MAC addresses could get wrongly accused, and false positives will only increase over time as people or software suppliers become more privacy concious. This is a bad idea because it is based on a false premise. It is reminiscent of the boneheads who insist that an IP address represents an unique user or geographical location. They're in denial because the truth would expose the basic fallacy upon which their "idea" depends.