Starting August 10, 2009 and valid until the end of August Microsoft will pay users to search and shop via Bing. When you shop online through the Bing search engine, Microsoft will refund you a portion of your purchase price at its own expense.
It is called Bing cashback (formerly known as Live Search Cashback) and they actually been doing this for a while, but now they will double that amount to up to 50% of your purchase price.
When a buyer searches for an item on Bing and then purchases it, Microsoft gets paid a commission for the referral. There are many sites that do this, but Microsoft is the only one that refunds 100% of this commission back to its users. What is really surprising is that Microsoft not only refunds 100% of the affiliate revenue to its users, but for the purposes of this ‘Back to School’ promotion, they will be matching these revenues at their own expense, effectively doubling Bing users’ savings.
This offer is only available to U.S. residents with Windows Live ID and cashback account.
Source: Bing