Twitter Inc.'s shares dropped 8% after Morgan Stanley reduced its rating on the stock to sell. The change in rating is based off the notion the micoblogging service will lose online advertising revenue to Facebook. Today shares fell as low as $63.50, since its IPO price of $26 Twitter has doubled its value. Scott Devitt; an analyst for Morgan Stanley wrote in a note "As competition for online ad dollars intensifies, we guide investors to Google and Facebook, dominant platforms with more attractive risk/reward,"