Amazon PayPhrase is a nice, risky step (plus some PayPal platform)

Today, TechCrunch posted about Amazon PayPhrase going live. It appears that Amazon customers were notified of this feature, allowing them to set a phrase they can later use on 3rd party sites to check out quickly - just type in your payphrase and PIN and you're out. The TC post mentions a similarity to PayPal's student accounts, I am not sure I agree, but that's not the case. The interesting question (one also raised in the post) is - what new risks does a new feature introduce into the system?

There's a lot to be said about modeling the possible risks in a new payment feature, and I find it to be some science, some art. You have to weigh not only what users and fraudsters are doing now, but also what opportunities will they have once you introduce a feature, and understand how to design controls that mitigate the major issues without hurting functionality. That's why there's some art in it.