Interesting question.

I can give you a counter-example, why I think that taxes shouldn't apply to generated coins: Let's say you programm an application (or paint a picture, etc.) and it is easy to estimate the market value. Do you need to pay taxes for your application (or the picture) as long as you don't sell it? IMO it's the same with generated Bitcoins.

I agree. But that seems a bit too intuitive for tax laws anywhere haha