Over 20 years, Peter Thiel quietly turned his Roth IRA into a gargantuan tax-exempt piggy bank. Using stock deals unavailable to most people, the billionaire took a retirement account worth less than $2,000 in 1999 and spun it into a $5 billion windfall. From the archives:

Lord of the Roths: How Tech Mogul Peter Thiel Turned a Retirement Account for the Middle Class Into a $5 Billion Tax-Free Piggy BankRoth IRAs were intended to help average working Americans save, but IRS records show Thiel and other ultrawealthy investors have used them to amass vast untaxed fortunes.www.propublica.org