Wow... there is some real bad info in this thread. Don't take anyone's word for it here, but use google, or better yet talk to an accountant. Zach basically outlined it.
You must pay taxes on all gambling winnings. The way your taxes are computed is on your total winnings. Your losses are taken as a deduction.
Don't guess or believe what you want from this thread. If you withdraw you leave a paper trail that could get you in a mess. 10k has nothing at all to do with it. http://www.onlinepokerfaq.com/guide/us-taxes.html
Oh and BTW.. you guys in the UK get a better deal on poker winnings that's for sure... but as to taxes in general.. whew boy.