how would IRS know what you mined?
Only if you identify your bitcoin address with your physical identification.
This retroactive law is illegal. Any law that is retroactive is illegal.
Also currencies are not supposed to pay taxes for themselves, only actives done to get income, having a job, making a sale, gambling, etc, but that is independent of the currency weather it is bitcoin or the dollar.
The dollar does not pay taxes, if you have $1000 dollars at home you do not pay taxes on the dollar, even if you have the $1000 at the bank the $1000 do not pay taxes only the interest made on the dollar. Why should bitcoin get a different treatment.?
The FED do not pay taxes on the newly printed dollars, why should miners pay taxes on the newly created coins.?
My opinion is that this law is not enforceable for independent miners, large mining companies will be force to go overseas otherwise they will not be able to compete at a global level.
In the town of San Ysidoro USA, the Mexican peso has high acceptance, and exchanges are anonymous and no tax is payed on the currency itself, a commission fee is payed for the service, and the exchange pays taxes based on the profit they make, but no tax on the Peso itself.
That double standard is hypocrisy, their real goal is to kill the currency.
There are a few good politicians that seem to accept it, but they are the minority.