A W-9 means you have to pay taxes on your win . The casino takes your SS # and gives you a form showing your win, and then the IRS get a copy so you have to report it as "income". (unless you win/loss statement at the end of the year negates it)...i hope i explained that where it makes sense.
I had a great win at 3 card poker, had played the bonus (I will NEVER not play the bonus again), I had A,K,J of clubs and the dealer had the Q, 10...so I won 1,000 to 1 on the bonus plus my ante and pair plus.
it was an amazing win...we finally came back from a trip to Vegas with MORE $$ than we took.