Fillet of Soul

Via Marginal Revolution and their "markets in everything": rent your soul for $25. I swear I'm not making this up. It's as easy as 1-2:

Step 1: Describe your soul….the more info you give, the better chance you have at renting it.

Step 2: We put your soul up for rent in the surrounding spaces. If someone rents it, we’ll send you the $25 at the PayPal address you supplied. It really is THAT simple! Don’t worry, according to the rental terms, your soul will automatically be yours again after three months, then you can rent it again, or keep it for eternity.

Which of course begs the question: what does someone do with a rented soul? And can there really be a flat rate for souls? Shouldn't some be worth more than others?