83 million Facebook accounts may be fakes: Facebook's share price has fallen below $20 for the first time, as it was revealed around 8 percent of its accounts could be sketchy. The social-networking website is now worth almost half what it was when it floated on the Nasdaq in May. It has lost nearly $50 billion in value -- more than the total valuation of Hewlett Packard or coffee company Starbucks. The stock debuted at $38 and since then has headed south, hit by increased doubts about its high valuation, growth prospects, and worries over its ability to make money from its growing mobile audience. Facebook's latest figures suggest as many as 83 million users may come from dubious sources -- including duplicate accounts, pages for pets and those designed to send spam.