I think as a good citizen should pay taxes on income earned during the year, as well as bitcoin you have to pay tax in accordance with the rules and regulations applicable in your country,...
According to the government a good citizen pays taxes, buys stuff on credit to indebt himself and his family, can't pay the loan back, so the property goes to the bank/state and allows government employees (lawyers, bailiffs) to make money at his expense. Do you want to be a good citizen? 
Normally your profits is the fiat coming into your accounts. Although the government would like you to declare everything, people in general don't count money received via random events because there's no way to track the flow of cash.
Examples of such events might be money:
found in the street,
won through gambling,
received as a gift,
earned from a small one-time job on the side like mowing neighbor's lawn, and so on.
