I recently read an article over at CNN Money that Amazon has now agreed to begin collecting sales tax in several more states, Pennsylvania now being one of them (my home turf). The other states listed to begin are: California (September 2012), New Jersey (2013), Virginia (2013), Indiana (2014), Nevada (2014), Tennessee (2014), South Carolina (2016). Amazon already collects tax in Kansas, Kentucky, New York, North Dakota, Texas, and Washington.
So it appears that Amazon has changed its position on the sales tax and is now going to stop fighting and slowly start collecting. Part of this change is that they want to have more distribution centers and other brick and mortar facilities in these states; another factor is that they want to increase their ability to do same day delivery. I am guessing that it will not be long before all 50 states will be clamoring for them to collect, as well as asking (requiring) other online retailers to start collecting.
I think we are seeing an end of an era. Pennsylvania is already asking on its income tax form if you ordered online and if you paid sales tax. If you did order online and did not pay, they ask if you have receipts (to prove how much you owe) or they estimate your tax based on your income. No more online tax holiday!