iTunes and tax

[AyuRox]

I didn't know if this should go in chat or gen. music... but anyways

what dictates wether or not you have to pay sales tax on iTunes downloads? I suppose this applies more to US residents... just because tax laws vary by country, and state, which brings me to my next comment. I looked a little into it online, and it seems that a common answer is that you pay the tax if you have a physical Apple store in your state. But there's been an Apple store in NC for years now, and i never had to pay tax until what seems like the turn of 2010. (I have a reciept from 12/22/09 with no tax, and one from 1/7/10 with tax, so I can only assume this came along with the new year) So, whats up? As if they weren't already cheating thier customers out of enough money???