tl;dr: 'Amazon will kill the retail store by giving up their unfair tax advantage and instead providing better service' http://www.slate.com/article...
"Giving up" their tax advantage or simply reading the tea leaves and understanding the states will eventually find a way to tax them? This is a government regulation avoidance move - not capitulating means spending gobs of money on people and processes to deal with 50 different tax laws.
- Ryan Kaisoglus