by the letter of the law, any income you have is to be reported and any tax due on that income paid...... ie: it's up to you to report the income yourself, even if no one else (
poker site, bank ect) reported it for you
go to irs.gov and do some reading, or consult a tax professional
as of right now, as far as I know, the
poker sites aren't issuing 1099g forms upon withdrawal of winnings
but if anyone has, or anticipates large withdrawals....it's a good idea to
document every penny .......
all deposits on all sites,
any money wagered anywhere like a casino, horses, dog track, lottery tickets.....everything.
that way you'll have a record of losses to offset any winnings...even go back and try to document past deposits at sites as well as losses at other live venues
the poker sites may not report things now, but with pending legislation, who knows what's coming.... it's possible that a new law could come into effect at the end of a year that covers the entire year (so some past withdrawals might get reported, and you'll be on the hook for any tax due)
also, your financial institution may report some deposits to the irs depending on amounts deposited, or certain methods of deposit (like depositing checks from poker sites or online payment processors)
something they dont do now, they may be doing in the near future, and past activity may come under scrutiny
in the end, if your not regularly making large deposits into a bank, and aren't withdrawing more than a few thousand per year.... not much to be concerned with......can easily offset a few k in winnings with losing horse, lottery tickets
(there's trash cans full of nothing but losing tickets anywhere near any betting windows 
)
