Investors should not necessarily look to Chipotle's example when deciding what to do. McDonald's (MCD -2.97%) stock has plunged following the release of some very concerning news. An E. coli outbreak involving its famous Quarter Pounder burgers spooked investors, and that sent the stock plummeting by 5% in the following trading session. The question for investors is how it affects the stock. Although Chipotle (CMG) recovered from a similar outbreak when it won back customers' confidence, investors should no ...