Google is taking a page from the credit card companies by incorporating an airline miles reward program as part of Google Checkout this month.As part of its quest to squelch PayPal, Amazon, and other online checkout widgets, Google last week said it was partnering with U.S. airline companies for American customers to get exclusive discounts and free shipping and earn frequent flyer miles.

From now until Dec. 31, shoppers who register to participate can earn two frequent flyer miles for every dollar spent through Google Checkout. Participating airline reward programs include Alaska Airlines, Continental Airlines, Delta Airlines, Midwest Airlines, Northwest Airlines, US Airways, and United Airlines. The miles are available for U.S. residents only.

In addition, Google is handing out holiday promotions from more than 100 of its retail partners. Some will give away free shipping while others will offer as much as $50 off select purchases.

Not to be outdone, PayPal's holiday offer includes even more aggressive incentives, like 20% cash back or no payments for 90 days. To prevent reward abuse, eBay is limiting rebates to $50 per PayPal account.

True, PayPal is more widely used than Google Checkout, though PayPal has fewer merchants -- albeit some of the largest ones: Barnes & Noble and Toys 'R' Us.

Still, Google says its Checkout Purchase History function trumps the competition. The feature lets customers track shipping status and purchase information. The search engine also has launched a "MyOrders" tab to its Google Checkout iGoogle gadget to make it accessible from any Internet-connected computer.

Forget any tracking or privacy issues here, having your purchase information available on any computer can be pretty awkward if you were trying to keep your shopping list a secret from your family. If you get caught, a trip to Hawaii or the Bahamas might let you off the hook.