I was perusing the IRS website (NOT for fun: I qualified in a local radio contest that has a "pick whatever you want" grand prize, which I will most likely not win; still, I wanted to be sure of the tax consequences in the unlikely event I do.) and I came across this gem in the "other income" section of the publication on taxable/nontaxable income:
Bribes: If you receive a bribe, include it in your income.
So simple, and so elegant. This has a flavor about it of "When did you stop beating your wife?"; if you don't include it in income, you are committing a crime, and if you do include it in income, you admit you have already committed a crime.
This of course begs the question: if you are involved in both receiving and giving bribes, are you able to offset the expense against the receipt as with gambling income/losses? Somehow, I think not...