Absolutely. Even the StreamLined Sales Tax Governing Board rules are not comprehensive. They have many different product categories, but they do not have them all. They pay various companies to provide sales tax data to Internet businesses, but the companies I've dealt with basically do the minimum possible and aren't terribly interested in improving. The bottom line is that if you want to be safe around taxes, you have to hire a lawyer and have them investigate the tax situation with your particular category of product in all the different areas it's going to be offered. Really, that's not something I envision anyone doing for free. It's not something you could just do once. Podunk, UT might have a city council meeting next week decreeing a 27% tax on your product/service with penalty of death if you do not charge the tax to your customers.