Well... here's a question from one of the Freepers not yet convinced 999 is the right choice: Will the 9%% sales tax apply to purchases made by the states? If so, what are the chances that states will raise their sales taxes to cover this loss of revenue?
Another tax avenue is another slippery slope for "we the people".
If you understand economics you will recognize that the cost of goods will decline by more than 9%. Unless a monopoly exists everyone including states will see lower costs even after paying the tax.