Although Boesky was small potatoes at $200 million by betting on corporate takeovers using inside information.
From Wikipedia:
He was investigated by the U.S. Securities and Exchange Commission for making investments based on tips received from corporate insiders. These stock acquisitions were sometimes brazen, with massive purchases occurring only a few days before a corporation announced a takeover.
NEW YORK (Reuters) ? Bernard Madoff, a quiet force on Wall Street for decades, was arrested and charged on Thursday with allegedly running a $50 billion "Ponzi scheme" in what may rank among the biggest fraud cases ever.
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