NEW YORK (Reuters) – Billionaire hedge fund founder Raj Rajaratnam and executives from some of the most prestigious U.S. companies were charged on Friday with the largest hedge fund insider-trading scheme ever.Investigators said they used court-approved telephone wire taps for the first time in a Wall Street insider trading case, sending shivers through the hedge fund industry which has traditionally picked up and shared trading tips to make big profits.At the center of the case are Rajaratnam,

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