Amazon's different because they're bigger than a rounding error, basically.
The principle is "same amount of taxes for everyone". I don't live in California but if I did, I wouldn't be huge on the idea of tax-disadvantaging local businesses against out of state businesses.
Then pursue the customers and force them to actually report their rightful use-tax when they file their taxes at the end of the year. Amazon isn't not collecting CA sales tax because they think it shouldn't be paid. They're not collecting the sales tax because they have no legal requirement to.
Except that they are not... a book on Amazon may cost $10 and a book at your local Borders may cost $10. At your local borders sales tax gets collected, and the book ends up costing $13. When you purchase it on Amazon you pay $10, and are then supposed to declare that you bought the book and pay a Use Tax. That Use Tax for a $10 is $3. You as a consumer are now obligated to pay the state $3.
Having a business collect sales tax for a state it has no presence in is not in accordance with federal law, and California law does not apply due to interstate commerce laws. Thus there is no way to force Amazon to collect tax for sales to California residents.
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Go tell the consumers to pay taxes for all of the stuff they have bought, it is the consumers who should be paying the taxes and aren't.
The principle is "same amount of taxes for everyone". I don't live in California but if I did, I wouldn't be huge on the idea of tax-disadvantaging local businesses against out of state businesses.