[ghaff]

And presumably work out some deal where they can transparently remit the sales tax on behalf of the sellers. That's probably the bigger deal than determining the amount which I imagine Amazon could do pretty easily.

In terms of what they sell themselves, they were well on their way to having a presence in every state anyway between warehouses, Amazon locker, etc. So they pretty much rolled on something that was going to be a moot point in a few years anyway.