Not accurate. For US federal taxes, you can deduct gambling losses against gambling winnings, but not against your income.

If you earn $50,000 in income, $X in winnings, and $Y in losses, you pay taxes on $50,000 of income, plus taxes on $X-Y of winnings (if it's a positive number).

You can only deduct them from your _winnings_, not income[1]. You can't go to Vegas, blow $10,000 on a single round of blackjack and deduct that at the end of the year.

1: http://www.irs.gov/taxtopics/tc419.html