A young, unsuccessful day trader from Spain, just got slapped with a tax bill to the tune of $172 million. The IRS said that he traded $500 million in stocks in one year, and since he didn't file, it is assumed that the gains have a zero cost basis. The trader was shocked at first and said "What's the IRS?" He eventually realized that the bill was real.
I assume that he will be filing a tax return now to get this cleared up.