I think the result of that would be relegating Bitcoin to small orders. Even then, Amazon would probably still face non-trivial problems with double-spending s

I think the result of that would be relegating Bitcoin to small orders. Even then, Amazon would probably still face non-trivial problems with double-spending schemes where someone tries to engage in large numbers of very small transactions as part of some larger fraud. The problem here is that neither you nor I can envision every possible way to exploit Amazon failing to confirm transactions of any size.