Microsoft is paying people to use their live.com search engine. Right now, they have a promotion with eBay which rewards Buy It Now Purchases that are paid with Paypal.
The percentage cashback is variable — it is currently at 14% — which can save you a bit of money especially if you’re picking up an MPC.
Maximum cashback per transaction is $200, at 14%, items $1428.00 and over will net you the $200.
Keep an eye out on Cashbackr to see what the current is. For more info, there’s a forum thread here.
Rules are here. There is a limit of 12 cashback transactions per eBay account.