I have a hunch that this will, in the end, be a massive win for large retailers vs. small ones. The task of figuring out how to calculate tax for all states is more or less the same amount of work regardless of size, which means for someone like Amazon it's more or less trivial, but for a mom-and-pop store it's a major hassle.
The South Dakota tax only applies if you sell more than $100k or send more than 200 shipments, which factored into the decision: Respondents argue that “the physical presence rule has permitted start-ups and small businesses to use the Internet as a means to grow their companies and access a national market, without exposing them to the daunting complexity and business-development obstacles of nationwide sales tax…
Consider selling 100x$1000 computers at $50 profit per each, vs 1000x$100 jewelry at $50 profit per each.