BOSTON ( TheStreet) -- U.S. stocks are vacillating between the positivity of strong earnings reports and the negativity of soft economic data. Short-sellers are on the prowl, looking to exploit weakness in heavy-volume names. Here are the 10 most shorted S&P 500 stocks. They are ordered by percentage of float sold short, from heavily shorted to most heavily shorted. If momentum picks up, these stocks could be susceptible to a short squeeze.