Let's Bitcoin takes off. Say you lived in the US and had an online service that dealt in the equivalent of ~20,000 USD or more income for you (personally). What are the laws for income tax on a currency like this? Can you get in trouble with the IRS by simply having tons of BTC that the market values at (currently) almost 5$ per BTC?
Of course you need to pay taxes for the state, but you can avoid that in a lot of different ways. But I think you should not avoid that, you will regret when discovered by the government.
Being a good citizen and honest, contributing to the country is an honor. Think positively and you will avoid more risk.