They will use the same court-approved reasoning that the feds use in the failed war on drugs. It's your computer, your house, your internet connection...therefore your house, computer and anything connected to it will be thiers to take from you. Whether or not you actually DID anything wrong is of no concern...welcome to 21st century Amerika.
Except computers are not illegal to own, and computers are often shared. It's not the same as drugs, where you would most likely have known that they were in your house/car/purse. How would you be expected to know if someone downloaded a few songs and left them on there for someone to share? It's not as though everyone checks that every day.