The concerns raised recently by Chris Hoofnagle at Electronic Privacy Information Center about Google's security do not bother me. From the postings at Google for Security Engineers I can tell Google is serious about security.
Note that Amazon has always been extremely cautious with customer data. The servers that store your one click data are not reachable from the Internet. There have been no incidents from Amazon.
It *is* possible to be secure. And I would bet Google is. A quick check of CardSystems' website reveals no security jobs.