Chairwoman Yellen, there is no social-media bubble By: MarketWatch July 23, 2014 at 06:00 AM EDT The important ones, including Facebook and Google, have earned their valuations, writes Tim Mullaney. Read More >> Related Stocks: Cisco Systems Facebook GX Social Media ETF Groupon Cl A International Business Machines King Digital Pandora Media Inc TripAdvisor Twitter, Inc. Yelp Inc Zynga Inc Cl A