There is a buy-it-now listing on eBay today where the seller is offering $630 in cash, which he will send electronically to the buyer through PayPal. The current price for this listing is $715. Why would someone pay $715 for $630 in cash?

Well, you may have heard that Microsoft recently launched a ridiculous “cash back” promotion in the hopes of bribing Google customers to switch to Microsoft’s search engine, Live.com. Seems some resourceful people found a loophole in the system.

Apparently, you can get a 10-35% cash back reward for all buy-it-now eBay purchases if you access the eBay listing through Live Search. So, people are simply selling cash and arbitraging the cash back reward. Your move, Ballmer.