Yellen's "stretched valuations" remark no surprise By: CNBC.com News July 15, 2014 at 11:43 AM EDT Fed Chair Janet Yellen highlights that some sectors, like social media and biotech, are seeing substantially stretched valuations. Read More >> Related Stocks: Akorn Inc Alkermes Plc Groupon Cl A Microsoft Pandora Media Inc Zynga Inc Cl A