Of course the BIG QUESTION is whether or not these 'trash' files are also depositing tracking or other malware on your machines or if they are simply collecting the addresses of the machines connecting to the torrents. One is questionable from a legal standpoint. The other is not.
Beyond that, this is merely confirmation of something we have suspected for a long time. I have compiled a list of some articles to send to parents I know which highlight the dangers of music downloading and sharing online, in the hope they can use the information to keep themselves and their children out of legal and financial troubles. So far; this is just grist for the mill.