Every day, Wall Street analysts upgrade some stocks, downgrade others, and "initiate coverage" on a few more. But do these analysts even know what they're talking about? Today, we're taking one high-profile Wall Street pick and putting it under the microscope...Shares of optical network equipment supplier Infinera Corporation (NASDAQ: INFN) have disappointed investors mightily over the past year, underperforming the S&P 500 by nearly 30 percentage points -- but one analyst expects that to change soon.This morning, equity research firm MKM Partners announced it is upgrading Infinera shares from neutral to buy and raising its price target 40%, to $14 per share.