Actually posession of child porn is a crime. If you live in the US, it would be very easy for the police to find your IP by setting up clients and monitoring traffic on the network and then check that info with your ISP, get a warrent, bust down your door and seize your computer. If there is child porn on your harddrive then you are guilty, buddy.

Of course I don't think they would go after you if you had only one picture, but if you had thousands of them, they would... they mostly try to catch the people who make/distribute for profit the stuff, though. Because without the people who make money off it, it wouldn't exist at all... Nobody creates content just to share it on P2P networks.

Actually a clever programmer could create a program that would monitor gnutella queries for childporn activity, then record the date/time/IP. The user could then complain to the pervert's ISP and probably get them banned. Of course this sort of vigilante justice is treading a dangerous path... I think the "middle road" of merley refusing to propagate the childporn queries is the best solution.