If you want to get really technical -
The state where I live has a mishmash of sales and use taxes. Sales tax covers only tangible goods. When it comes to digital downloads, the Powers that Be have declared that use tax applies to software downloads, but no other kinds. The idea, as I understand it, is that software programs are tools that are "used" by the purchaser in a way other downloads aren't. Fine with me at this point, as all I offer for download are graphics images. My state also considers my place of business to be the location where the transfer takes place, so from its point of view it doesn't matter where the downloading is done. Some customers could live in states that look at that differently.
I'm actually thinking of moving to California, although not for several years. This tax alone wouldn't change my mind - but, then, if I do move it'll be for family reasons that trump the negatives of paying a use tax. IMO, the cost of living in California would be more of a financial burden than this tax would be.