The sale would take place in the state that the seller is located in, not the buyer. At the very least it would be less work. One state tax code to deal with instead of 50. The bonus is that most online retailers already have to collect tax for in state purchases.
Is "location" defined by the jurisdiction where an incorporated entity of some description is registered? Or where the business owner maintains residence? What if there are multiple owners; then, which one? Is it about where the servers are hosted?
All these attributes can be moved around; I live in Georgia but can register my corporation in Delaware. I can host my servers in Norway. And so on...