The Guardian has an interesting story on the rise of child pornography on P2P networks (Race to save new victims of child porn). Rather than simply bemoan it, the article points out how it has increased the ability of police to investigate. The main problem seems to be that there are too many targets to investigate, not that they can't be found. The article quotes David Wilson, professor of criminology at the University of Central England in Birmingham, as saying that,

The achilles heel of peer-to-peer is that it makes something that is secret and furtive into something that is public and when it is public that offers the police a window of opportunity to police it.

Indeed, the article goes on to note:

Paedophiles believe it is harder for them to be detected through peer-to-peer software but investigators are able to access their shared folders and quickly discover if they contain illegal images of child abuse. They are then able to establish the location of the owner of the shared folder. ....

By exposing themselves to public gaze via file swapping services, paedophiles whose abuse may never have come to light are now more likely to be caught.

Before, police would have to conduct a raid to find the amount and type of child pornography on a suspect's computer. Now, they can browse the suspect's shared files from the precinct house and learn a lot more about what their suspects have been up to (and how dangerous they might be).

Of course, some worry that pedophiles will switch to encrypted networks. Perhaps, but that means it will also be harder for pedophiles to find and provide support for each other. Either way I think this is a win for child porn opponents.