It happened almost every earnings season. My hedge fund would own a million shares in some company and two weeks before it was to report quarterly earnings, its stock would start dropping. There was no news to explain it. We were in the dark, even though it was my job to know. Inevitably, the company would report a disappointing quarter, missing Wall Street's earnings expectations by a penny or two. Someone knew. A salesman's brother-in-law heard a few deals didn't close. Or maybe an insider was singing.

The recent arrest...