Well, you knew it was coming. Even though Google Checkout isn't much aimed at being a threat to Ebay's Paypal, the gauntlet has been thrown down: Google Checkout is on Ebay's non-accepted payments list
Though we're betting Google isn't bursting into tears over the rejection, it does limit their free advertising a bit to not be accepted on the world's largest auction site. Where it is likely to hurt most is the level of small businesses that also use Ebay to sell some of their products.
Google Checkout is targeted more at the small business person, but it is not always advantageous if you have to have two companies to receive payments from. Of course, that means that this double-edged sword could cut the other way, where more volume-oriented business sellers pull their products off of Ebay instead.
Whether this will end up being a detriment to Ebay, Google, or both is still a mystery. But rather than speculate that, we'll leave you with a better question: If you look on Ebay's list for why a payment method is disqualified, there isn't an easy answer for the removal of Google Checkout. We suspect there is a simple answer - Ebay owns Paypal, and it doesn't want a competitor muscling in, no matter how small the perceived threat.
Got a guess as to why Ebay banned them? Can you fit your reasons within their declared policies? We'd love to hear them in the usual spot