Also, I wish people would quit calling this a new tax. The only difference is who has the burden of reporting.
Current law in most states requires you to pay sales/use tax on items purchased from out of state, but the consumer is expected to report this. However, nobody does, so now they're trying to enforce reporting on the merchant side.
In theory, not paying sales tax at the end of the year on items you purchase over the internet is tax evasion. It is, however, like going 66 in a 65 zone. You're not likely to get prosecuted.
The California State board of Equalization says
If you make such a purchase and then use, give away, store, or otherwise consume the item in California, you may owe California use tax. This is true whether you order the item over the Internet, by telephone, or by mail. The use tax rate for any California location is the same as the sales tax rate. ... If the out-of-state retailer does not collect the California tax which is due on your purchase, you are required to report and pay use tax