IPO Millionaires: The Few, The Proud, The Unbelievably Lucky

News of Twitter's IPO comes with the obligatory story about how many people of modest means have instantly become millionaires: an estimated 1,600, according to the San Jose Mercury News. These are employees -- largely engineers -- who got stock and whose net worth is now, at the minimum, into seven figures.

That is, seven figures on paper. But if you're thinking of taking a job at the Next Big Opportunity, it's best to realize how rare the chance to cash in is and how many things can go wrong, even if you wind up at the right company.