The Internet sales tax bill should push business back to brick & mortar in a lot of areas. Why pay taxes + shipping when you can drive a short distance and support local?
In theory though, internet businesses should be able to compete. They should, in theory, have less overhead. Companies like NewEgg compete with Best Buy, do tremendously more sales, have way less floor space, a much broader selection, and far fewer employees. They do have the overhead of expensive servers and things like that; but I think they can still compete.
Hopefully though, it will drive 'parasitic' buyers to buy. Buyers who shop local, but buy online. Nothing wrong with buying online, but you take the good with the bad. If you try it on at the store; you ought to buy it there; else it'll be out of business and you'll be forced to buy sight unseen!
It's getting harder and harder for me to find helmets and motorcycle gear locally because most shops just aren't carrying them. All people do is come try it on, find their size and fit, then go order it online to save $10+tax.
I have a feeling that more online retailers will offer free shipping in order to remain competitive. They'll work it into the retail price; so chances are prices won't actually be cheaper than in store. So what it'll come down to, is at the end of the day, it'll cost the same at a brick and mortar or online. Advantage of online is shop at your leisure, and usually a broader selection; plus no need to drive. For example, even if I would get Meguiars UC the same price at Wally World as I do Autogeek, Wally World still isn't going to carry DP, Wolfgang, Chemical Guys, etc. Companies like AutoGeek will make free shipping 'standard' and just match the prices to MSRP (giving them a broader margin because of less overhead to pay for the shipping), and we'll be inclined to even buy the OTC stuff just for the convenience of getting it all at once. If all I need is some CG clay lube, well, I'm already here and already got the credit card out, so I might as well buy my towels and Meguiars products and whatever else I could've gotten locally at a parts store or box store.
My $0.02. Personally don't think much will change with the online sales tax. With the exception of the 'try then buy elsewhere', which is a good thing. (Because they'll have to have driven there to try it on, price will be similar; so why not.)