No, no, no you’re doing it wrong. The sales tax requirements would be limited to states where that business has a particular physical presence so unless “mom and pop” Inc is located in 49 states, they wouldn’t be concerned with any other states than the one that the reside in.
One of the reasons that Amazon is mentioned so frequently is because they have large distributing facilities in a variety of states and as a result would be subject to a larger overall impact...not that they wouldn’t pass the cost down to the consumer of course.
You are describing the law as it stands today, not what Amazon is pushing, and what is currently moving through congress (was Main Street Fairness Act, now is Marketplace Fairness Act). The proposal is that all online sales would be taxed, regardless of physical location. Now that Amazon is in more and more states, and having to pay sales tax, it is now a competitive disadvantage to other online sellers that are in a single state, so Amazon is helping get everyone taxed so they are not at a disadvantage. That's why they are doing these little one or two year deals with California and New jersey - they are just stalling while waiting for the national legislation. This article has a good explanation of what is going on:
http://seekingalpha.com/article/530681-amazon-s-billion-dollar-payday-nearing-thanks-to-marketplace-fairness-act