"The Congress shall have Power... To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes;" -The Constitution
A state trying to regulate what is fundamentally interstate commerce is not only illegal -- it's unconstitutional.
Ordinarily, lawbreakers are punished. I would suggest that many citizens in your states could be outraged to learn that their elected reps are spending their tax dollars trying to break the law, and make life more difficult with a steeply regressive tax. I suspect those citizens would seek to punish those lawbreakers in a variety of ways -- including, when applicable, at the ballot box.
And I suspect that many of those outraged citizens would include those who worked online for a living -- a far greater number than you may realize -- who happen to know how to use the Internet for all sorts of things, including rallying ad-hoc campaigns.
For example, Utah's state reps and senators found out an unpleasant truth during this last legislative session: Utah has 10,000 "mommy bloggers" who were outraged to learn that their lawmakers were trying to attach taxes to affiliate advertising with companies such as Amazon. And, it turns out, bloggers are easily outraged, unified, politically active, and love nothing more than to blog profusely about things they are upset about, including specific state reps. (The proposed law was scrapped, along with a few legislative careers, I suspect.)
Just, you know, an FYI.
