Consumerism Commentary runs down the weirder wrinkles in the US tax code, including the rules governing bribes and the stuff you own, but which does not belong to you:
Q. This year, I’ve been taking bribes to keep the caviar smuggling ring off the FBI radar. Do I have to report this?
A. Yes. If you receive a bribe, include it in your income...
Q. I found an abandoned car and kept it while the person who lost the vehicle presumably wept. Do I have to report this?
A. Yes. If you find and keep property that does not belong to you that has been lost or abandoned (treasure-trove), it is taxable to you at its fair market value in the first year it is your undisputed possession.