Originally Posted by DamianJ

That's only the start!

a) How do they prove that the person paying for the IP downloaded the file?
b) How do they prove the file was actually downloaded?
c) How do they prove the file was actually what they claim it is?
d) Have they not heard of IP Spoofing?
e) Have they not heard of unsecured wifi?

Basically, you can't prove it. You would have to go to the guy's house, get all of the computers in there, find the file he allegedly downloaded and show the court that is your copyrighted content.

Far too much trouble. Miles better to just blackmail fans of your work and potential customers and hope to get some hush money out of them.