There is sometimes confusion over sales taxes and when they are owed. Basically under the current laws a retailer is required to collect a state sales tax:

1) If they have a business presence in a given state.

2) If the customer takes delivery of the goods in that state.

My store, for example, is only in Virginia. Therefore I only collect 5% VA Sales Tax (by law) for any sale made in Virgina AND the customer takes delivery of the goods in the state.

Out of state buyers are NOT exempt from their state sales taxes, its just the merchant may not be collecting them on behalf of the taxing authority. You still are required to report your out-of-state purchases to your home state and submit a Use Tax on them (equal to your state's sales tax). No one ever does though, unless they are running for public office or work for the Justice Department, etc.

States are scrambling for revenue right now and know they are losing millions in sales taxes from out-of-state purchases. They are looking to get that money on goods purchased and making headway. One of the most ardent champions of defending the sales tax status quo has been Amazon.com. However today I about fell out of my chair when I head on the radio that Amazon has agreed to begin collecting Virgina Sales Tax in September 2013 in a deal worked out with the Governor's office. They are opening two distribution centers in VA (this gives them a business presence in the state) so in another 18 months - Amazon will begin taxing its VA customers.

I think you will see more of this, and the days of not paying sales taxes on out of state purchases may be winding down.