As reported in Under the Dome:
The move would allow the companies to avoid having to collect sales tax on sales to customers in the state. Under the commission programs, the .coms pay a percentage to Web sites that steer buyers to the online product.
Overstock's move is in response to the proposed "Amazon tax" included in the NC House budget plan.
The proposal would use the commission arrangement to justify levying sales tax on Internet purchases. Current state law already requires North Carolinians to pay such a tax, but taxpayers have to report themselves. Few do.
What does that mean for NC? More unemployment, as those in the associate's program for Overstock and Amazon will be out of work. Less income tax, as the associate's lose income they were earning from the commission program – there is less income to tax (remember, we're in a "budget crisis"). Less economic activity, as less income also – and more importantly - means less money to spend and invest in North Carolina's economy.
Expect many more online retailers to join Overstock.com and Amazon in cancelling their affiliate's program in NC. Have a look at this list of merchants who pulled out of New York after that state enacted the tax NC is currently considering.