AuctionBytes discovered that eBay bans sellers from using Google Checkout to request payment. One of their official reasons is that Google Checkout doesn't have a "substantial historical track record of providing safe and reliable financial and/or banking related services." Google says they had a lot of experience from AdWords and Video Store payments. It's interesting to note that eBay accepts "PayPal, credit cards including MasterCard/Visa /Amex/Discover, debit cards and bank electronic payments online for eBay purchases". Google Checkout is just like using the credit card, but through a Google proxy (that removes personal information and helps you if you don't trust an online store).
In a related note, Reuters reports that PayPal President Jeff Jordan will leave the company in the following months "to spend more time with his family". He must've come with a better reason than that.
While eBay tries to face the increasing competition with anti-competitive practices, Google has a much more relaxed attitude and says "We want to work with everybody".
Google Checkout review
Former PayPal engineer predicts Google's end