If I understand the question, in order of safety
- Never provide your cc or bank info to Google
- Provide Google with a rebate or gift card number
- Use a virtual cc number
FYI, in a moment of insanity, I used Google Checkout many years ago when they were offering all sorts of discounts and never suffered any ill effects … other than a sore backside from the many times I kicked myself for trading my info for a handful of silver.