Makes (ad)sense to me: (From the Wall Street Journal (free feature):
“(Google, which) has terrified Silicon Valley with its ability to quickly create new consumer products and services, is developing a rival service called GBuy. For the last nine months, Google has recruited online retailers to test GBuy, according to one person briefed on the service. GBuy will feature an icon posted alongside the paid-search ads of merchants, which Google hopes will tempt consumers to click on the ads, says this person. GBuy will also let consumers store their credit-card information on Google.”
Since they know your IP address, your home address, your phone number and everything you search for and click through, even what the roof of your house looks like, it only makes sense that you’d also give them your credit-card information.