This is going to increasingly become common esp as governments try to cover budget gaps. We just went through a sales tax audit for our SaaS company and so are expecting a good size bill for taxes not paid + penalties. Yes - fun stuff. Honestly, the gov't folks are playing whack-a-mole here trying to keep up with fast-growing areas that don't fit the old "you sell this widget for $X" model they're used to. And so the…
I stopped working with a client already over this. Simply put, cash-flow wise I can't currently risk taxes and penalties. It turned a customer into a liability because of the horrible wording and unclear guidance (seriously, they want us to pro-rate by the % of our software used in the state?). I suspect many other small start-ups will make the same choice we did until this all gets sorted out.
Personally I read that it's kind of like sales tax, and buying online. If the seller doesn't do business in the state you reside it's up to the purchaser to pay the tax.