Top executives of New York-based hedge fund manager Platinum Partners were arrested on Monday and charged with running a $1 billion fraud that federal prosecutors said became "like a Ponzi scheme" as its largest investments lost much of their value. Led by Mark Nordlicht, Platinum was known for years for producing exceptionally high returns -- about 17 percent annually in its largest fund -- by taking an unusually aggressive approach to investing and fund management, as detailed by a Reuters Special Report in April.