Curiosity Questions - IRS and Income Taxes

I've always been curious about how the pro player's handle income taxes. When you play in a major tournament (ie. The WPT) and make it to the cash, does the tournament or casino have to get your SSN and report to the IRS how much they payed each player? If not, do any of the players (like those on the bottom who may only make %15k - $20 k) take their winnings in cash? If you deposit a big check your bank would have to send in special forms to the government.

Also, do many of the top pro's who mainly play in cash games ever get "Lifestyle audit's) by the IRS? Is there any sort of audit trail in the big cash games? ie. If Doyle Brunson comes into the casino and gets $100k in chips at a cash table, does he come in with the actual cash or can he write a check to the casino? Does he do a cash advance on a credit card? Maybe get a credit line with the casino?

Just curious how the pro's handle the large sums of cash they're involved with what kind of income reporting pro players have to do. Thanks.