Most developed nations have some for of consumption/sales tax. In the EU it's typically 17.5-25%, in Australia it's 10%, in Switzerland it's ~7% and so on. America has this on a state by state basis.
Nowadays the split jurisdiction with interstate commerce is now awkward and unwieldy. I believe that in the coming years the Federal government will act to enforce an interstate sales tax and maybe even a tax on imports. The path of least resistance here is for the sales tax due to be the sales tax that applies in the state of the recipient.
I'm not sure how much revenue that would raise but my guess is a lot.
As for Amazon, I'm not sure what they're thinking. In a year they'll have the same problem. One would think they're confident of Federal action in the next year on online sales taxes or they think the climate will have changed in a year. I'm not convinced of either. Are they that desperate that a year's delay is a win for them?
While we're at it, what's up with New York? Amazon collects sales tax for the state of New York while it (thus far unsuccessfully) has tried to challenge the "Amazon tax" in the courts. Is New York a test case? Are the affiliates in New York that much more valuable?