Groupon shares tumble, as H-P rally fizzles By: MarketWatch February 21, 2014 at 12:37 PM EST Groupon tumbles after the company reported a weak forecast; H-P’s share rally fizzles amid worries that it’s recent momentum may not be sustainable. Read More >> Related Stocks: Groupon Cl A Hewlett-Packard Juniper Networks PHLX Semiconductor Sector Index