yes. Any gambling win > $600 or a win over some multiple of your initial wager is taxed by the feds (and many states have additional taxes). Professional gamblers can write some portion of their losses off against that tax (I'm not sure of the details, you'd generally need to hire an accountant to handle something like that).

Source: I used to work in the gambling industry and have had a win large enough to be required to pay significant (>$3k) taxes on it.