What is Google Checkout?
Google Checkout is a faster, more secure way to buy from stores across the web using a single username and password. Use it once and stop creating new accounts every time you buy. 
You do not have to join Google Checkout in order to pay with it.
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What is PayPal?
PayPal, a leader in online payments with over 193 million accounts worldwide, is the faster, safer way to pay and get paid online. PayPal makes online shopping fast, fun and easy, and it’s accepted by thousands of merchants all over the world. With PayPal, you don’t have to worry about exposing your financial information – PayPal never shares it with merchants.
You do not have to join PayPal in order to pay with it. 
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