In my country (Australia) ALL gambling winnings and profits are 100% tax free.
You don't have to declare it because it is considered a hobby.
In the USA and other countries gambling winnings are treated the same as income and gambling companies are required by law to withhold federal income taxes.
And those are the benefits of living outside U.S.A as a gambler where your gambling winning aren't been taxed. Because to me, it's kind of unfair that you will be taxed a certain percentage when you win in his country, but fails to compensate when loses while gambling, as the genuine people that ought to have been taxed are casinos operators or owners, since casinos are businesses which offers essential services with the aim of generating profits. However, base on the tax related issue in U.S, this is likely to be an advantage to Bitcoin, as due to the tax of been tax, many U.S citizens are likely to prefer Bitcoin casinos whose winning are always tax-free.