So a single banner ad or book review placed on a blog by a single person in a given state in the USA constitutes a "business presence"?
Not exactly. The Supreme Court previously ruled that a state cannot collect a sales tax on sales made to its residents unless the seller has a nexus in the state. A nexus usually means a physical presence such as a retail store, a distribution center, etc.
The NC legislature is attempting to implement a new law that says that if the seller has online click-through affiliates in the state meeting certain criteria, then that constitutes a nexus. So then once the nexus is established, the state can start collecting sales tax on all sales made by the seller to residents of the state, whether the sale was made directly by the seller or via an affiliate link.
Maybe I'm dumb, but no money changed hands in NC.
It doesn't matter to the politicians. They see an opportunity to raise revenue. It doesn't matter to them whether money has changed hands in NC.
How is a nationally targeted website maintained by an NC resident different than a magazine sold with an ad that generates an NC sale?
The ad in the magazine was probably placed by the seller, not an affiliate.
However, that may be next on their list.
I see opportunity for someone to set up a site/blog blasting the latest news on the these developments.
Perhaps helping small affiliates navigate the LLC process in a "good" US state and charging a reasonable fee.
You'll want to consult a qualified attorney and/or accountant. Based on my reading of the legislation, it's not based on whether the affiliate is based in the state, it's whether the affiliate is a citizen of the state.