As far as I'm concerned they are perfectly welcome to snoop to their hearts content, as long as they don't waste network resources to do so. I have no intention to track down individual nodes which perform that perfectly acceptable and legal task.

I don't share anything I don't have permission for and I advise everybody to avoid sharing huge collections in any case. This sharing network is far better served by the few who share original content than by the many who have huge collections of the same old commercial product as hundreds or thousands of others.