Not having the chance to try Google Checkout as a Canadian merchant (it wasn't available to Canadian merchants at the time we made our payment solution decision), I'm reminded of a very early quote from Max Levchin when he discusses one of the first years after Paypal launched.

The quote attributed almost the entire first year of Paypal to fraud. Running and managing 3 CPA campaigns I can now understand why, it seems like everyone with a (stolen) credit card tries to extract the money through online scams.

It should have been clearly visible at the time that choosing Google Checkout would have been a risky decision as a merchant because Google was going to inevitably go through some of the same growing pains. Luckily for us, we dodged that bullet - but by no means is payment integration and fraud detection easy.