Paying with Amazon is mostly frictionless for me. If I remember correctly from my purchase on louisck.net on Sunday, it was click to get to Amazon login page, click to login to Amazon account, click to use card ending in 9432, click to confirm.
And, correct me if I'm wrong, they've been delivering that level of convenience for many years and without any need for iframes.
All due respect for Stripe, iframes are a potential security hole waiting to happen. iframes open many possibilities for exploits. I doubt we've seen all of them yet.
