On a mild evening last January, federal agents met Ramesh Chakrapani as he stepped off a plane at New York's John F. Kennedy International Airport. The 33-year-old Blackstone Group banker spent the next three nights in a Manhattan prison cell, charged by the Justice Department and Securities and Exchange Commission with tipping off a friend about the 2006 acquisition of grocery-store chain Albertson's.

Blackstone immediately suspended the London-based Chakrapani, who was accused of using phone calls and text messages to alert the friend, a financial analyst who allegedly made $3.5m (€2.4m).