According to a survey released today by e-mail security firm Proofpoint, 33 % of U.S. companies with more than 1,000 employees have people on staff whose primary or exclusive job is to read or otherwise analyze outgoing e-mail messages. 18 % investigated the exposure of confidential company information via video or audio posted to a site such as YouTube; 17 % investigated leaks of company information posted on social networking sites such as Facebook; 13 % looked into leaks sent via SMS text or a tweet on Twitter. 41 percent said they are “highly concerned” about the risk of information leaks via Twitter. Story on ZDNet.