As for the rest of you ( and sageecl ), you should always
be in control of what you share.

Some P2P applications share the downloads folder by
default, but you can easily change that. It has been a
longstanding problem that some junk files and worms
spread easily simply because so many people are sharing
their downloads without first checking what they actually
have.

Also, don't forget to check the advanced settings for sharing
of partial files, which enables your software to share bits
and pieces of your downloads even before they are
complete files on your own disk. Most software comes with
this enabled by default too.

If you take care of these two details there's no way you can
ever be sued or charged for sharing anything you didn't
intend to share.