Be careful before you open up that next e-mail from your boss. According to a new survey, 10% of U.S. employees report their company has used e-mail to fire or lay off employees. Hey, it could be worse for those 10%—at least it wasn't voice mail. The online survey of 752 U.S. office workers, conducted by Harris Interactive for the Marlin Co., also found that 17% of respondents said their boss has used e-mails to avoid other difficult face-to-face conversations. "E-mail has become the new shield of today's business. Companies hide behind it to avoid the negative reactions of unhappy employees," said Frank Kenna III, president of Marlin Co. The survey also found that 5% of respondents said they had been the recipient of a humiliating e-mail that was copied to other individuals; 23% of workers said they have received a politically incorrect e-mail; 15% said they had been the recipients of an e-mail sent in anger; and 13% reported receiving flirtatious e-mails.