If your computer's connected to the internet, odds are you've received countless virii-burdened emails that read, "Dear Sir/Madam, we have logged your IP-address on more than 30 illegal Websites. Important: Please answer our questions! The list of questions are attached."
One very smart fellow in Germany received the German version of that Sober.Y spam, then, presuming it was real — turned himself in to authorities. The polizei examined his hard drive and discovered an abundance of kinderporn.
Link to synopsis on f-secure, and here is the original report (in German). (Thanks, Ben the Geek)