Excerpt: For Merck & Co., one trigger was the withdrawal of Vioxx from the market. For Marsh & McLennan Cos., it was news that New York State Attorney General Eliot Spitzer had launched an investigation into alleged bid-rigging. And for Delta Air Lines Inc., it was simply investors' belief that management had mismanaged the company. The result for all three companies, however, was the same: after their stock price fell precipitously, employees hit them with class-action lawsuits citing[.]  MORE >>