If you earn money with anything, you'll have to pay taxes. But the tax must also be reduced in the case you loose. These mechanisms should also be valid for virtual currencies. But first this must be legalized.
This doesn't make me happy, but is fair ;-)
How do you see this being implemented? How will they tax Bitcoin of millions of people?
Today billion of people pay taxes.
When you registrate at a trading platform you have to tell your tax identification. After that all tax relevant informations will be sent to your fiscal authorities.
Very easy and not really big data ;-)