The laws may have changed, but it used to be you were charged sales tax for internet purchases only if the company from which you made the purchase had a physical presence in your shipping state. Washington state would definitely count toward a tax from Amazon because Amazon ihas a physical presence in Seattle. I'm not sure about California.

In the past couple of months I've purchased two Kindles and numerous ebooks, and not once was I charged sales tax--thankfully. The ebook purchase tonight was the first time. I wonder if the publisher of the book matters?

[edit]I must have posted the same time as JMikeD. His post seems to answer my publisher location question.[/edit]