They currently collect sales tax in 24 states[1,2], and I'm guessing the writing is on the wall in the other 26. I don't know if there's any truth to this Radio Shack rumor, but I'd expect that avoiding tax nexus status probably isn't as big a deal for them as it used to be, because they're going to be forced to do soon, one way or another.

[1] http://ilsr.org/rule/states-amazon-sales-tax-map/

[2] http://blog.taxjar.com/michigan-sales-tax-nexus-law/