There are two types of taxes you need to worry about with Bitcoin.
The first is regular income tax. If you earn bitcoins by mining or doing any other kind of work, you must declare the market value of your bitcoins as earned income whether you sell them or not.
So you are telling that if i draw a great painting, i must decrale its market value as earned income, whether i sell it or not?
No, because that painting isn't payment for services rendered, which is what mined bitcoins are. They are the payment that miners receive for securing the Bitcoin network. If you receive
anything as a
payment for services or any other kind of work you did, that's income and you have to declare it.
So if someone pulls off a 51% attack he also gets tax free bitcoins?! That's unfair...