The only thing different between the "mail order age" and the internet age is the relative amount of commerce occuring via the latter. You're absolutely right

The only thing different between the "mail order age" and the internet age is the relative amount of commerce occuring via the latter. You're absolutely right that the main difference is the astronomical difference in scale, but you're ignoring the fact that internet sales are entirely on-demand, whereas mail order sales still require a physical catalog to order from. This may not sound like a significant difference, but the instant-on internet fundamentally altered the way the public buys the majority of its goods in a way that mail order businesses never could. This is what I meant when I said that the government didn't change its laws to reflect the reality of the internet, and it's why Quill v. North Dakota isn't a great example of today's reality. Personally, I think the problem is a simple one to solve by doing what Illinois (where I live) did this past year with its tax form -- basically, you had two options: you could either a) calculate what you actually paid in sales taxes via receipts and whatnot, or b) divide your income by some small percentage, and choose the higher of either that number or $50. (Or something like that.) The kicker was this instruction -- Do not leave this blank. (The irony, of course, is that Illinois passed an "Amazon tax" law of its own earlier this year.) Since no one wants to be audited, I'm sure the rate of compliance was pretty high.