One study by Laura Frieder of Purdue University and Jonathan Zittrain of Harvard University, found that the stocks mentioned in those otherwise annoying emails experienced a huge price increase, as well as a big jump in volume, after the messages were sent. Clearly, investors’ skepticism is being trumped by an eagerness to believe. As Zittrain told me: “Greed all too easily colors our objectivity,” and this is true for all types of investors.

Source: Why the Twitter hoax suggests the stock market is near a top – MarketWatch