Can you imagine your Data Leak Prevention system not being perfect? Is there value in a service that scans P2P networks looking for leaked data that eluded your Data Leak Prevention (DLP) controls?
Tiversa offers such a service. In an example of the value of their service, according to a Washington Post article, they claim that "the personal data of tens of thousands of U.S. soldiers - including those in the Special Forces - continue to be downloaded to unauthorized computer users in countries such as China and Pakistan..."
On a separate, but possibly related note, there was an Ars Technica article last last week on a bill working its way through Congress called the "Informed P2P User Act." From the Ars Technica article:
"First, it requires P2P software vendors to provide "clear and conspicuous" notice about the files being shared by the software and then obtain user consent for sharing them. Second, it prohibits P2P programs from being exceptionally sneaky; surreptitious installs are forbidden, and the software cannot prevent users from removing it."
It's clear that P2P represents risks that can be reduced by both technical and legal means.