There are, of course, pitfalls. More than half of all start-ups fail within 10 years. "It's not clear yet whether the wisdom of the crowds will hold for picking successful businesses," says Josh Lerner, a professor of investment banking at Harvard Business School. Investor losses could lead to big disappointments, litigation, or, worse, allegations of fraud, says Bryan Sullivan, a lawyer in California. "My mother is a secretary," he says. "My father is a construction worker. Those are the kind of people who would throw $5,000 in and think they can make $100,000. What happens when it fails?"