Neither should be favored. If a customer that lives in each of the 50 states walks into our retail store, we still only have to collect a single sales tax and remit it to a single entity. If a customer that lives in each of the 50 states logs into our online store, we have to collect 50 sales taxes and remit them to 50 entities. That's a law that favors retail store owners over online sellers. A law with the same practical effects could be written that favors neither by having a single federally-operated sales tax that's distributed to the states according to the relative sales volume to residents of those states.
