When questioning the White House claim that some sensitive e-mails from officials there might have disappeared for good, Democrats can cite any number of high-profile computer users who once thought the same — from Oliver North to Bill Gates. “You can’t erase e-mails, not today,” said Sen. Patrick J. Leahy (D-Vermont). But security experts interviewed Friday disagreed. As the number of e-mails sent has soared, they said, companies have become more rigorous in wiping out old records. As a result of the increased hassle and storage costs, electronic messages that used to last on computer servers indefinitely can now vanish after a month. “You cannot make the assumption that all e-mails today are kept somewhere,” said James Butterworth of Guidance Software Inc., which makes computer forensic tools…
