This seems like it is equivalent to "remote API key" that sites like Friendfeed provide, in that you don't need to give your amazon password to the other site.

This seems like it is equivalent to "remote API key" that sites like Friendfeed provide, in that you don't need to give your amazon password to the other site. It's kind of like a disposable credit card number in that respect. It could use a different name and a better explanation, though. Additionally, I can't even list a site where I'd buy something using Amazon's payment gateway where this would be useful -- there just aren't as many as those that use, say, paypal.