How can you get a jailbroken iPod touch?

On sites such as eBay and CraigsList, there are some people who sell jailbroken iPod Touches. You cannot get a jailbroken iPod Touch from a regular retailer, but you can jailbreak an iPod using various other sites (links will not be posted because jailbreaking can allow downloading of all apps for free, which is illegal, and WikiAnswers will not aid in criminal activity).