When he becomes president, Barack Obama will have to give up his BlackBerry. Aides are concerned that his unofficial conversations would become part of the presidential record, subject to subpoena and eventually made public as part of the country's historical record.

This reality of the information age might be particularly stark for the president, but it's no less true for all of us. Conversation used to be ephemeral. Whether face-to-face or by phone, we could be reasonably sure that what we said disappeared as soon as...