Tax law is dependent on your country and locality. Recently in the United States, the IRS has declared that Bitcoin is to be treated as property, not currency, for tax purposes. All income in the US is taxed, regardless of what form it takes. If youre paid in bitcoins, youre supposed to pay taxes on your earnings at the BTC/USD exchange rate when you receive payment.
Is it a good decision or bad?
Yes , many countries which has legalized bitcoin and other crypto currencies has also regulated it in a way of imposing a tax on the transactions just like fiat .
This is a policy that government has to follow to maintain the flow and record of the money an individual is making .
Moreover , it is just a way of acceptance by the authorities which is needed .
Paying tax on BTC, is a win win situation for us. There are some countries which do not want to legalise the bitcoin. So, they are deprived of getting tax. If they want to get more tax then they can legalise the BTC also BTC will get new market.