This is much more likely to be a desperate attempt by Google to stem the massive amounts of fraudulent AdWords activity. Having worked for a company who utilised AdWords heavily, the amount of times the company credit cards were compromised was frankly mind boggling. Every single time, the initial response form Google was that details must have been harvested elsewhere on the web. Once it was pointed out that certain cards were exclusively used for AdWords, their policy changed somewhat.
Was Google's customer database being ransacked by unchallenged villains ? They would certainly never admit it, but the evidence is both overwhelming and really quite damning.