It's a dangerous scenario. Employee blabs sensitive information over e-mail, and before long, it has circled the world thrice over. The folks at San Francisco's Disappearing Inc. (www.disappearing.com) think they have a solution. Their e-mail service, scheduled for release in March, automatically destroys messages after a set time, be it one or 90 days.
Disappearing messages are regulated by encryption keys. Every time the message is read, it must first access an encrypted key--a bit of software--on a Disappearing server. When a message expires, the key and the message are destroyed. Poof!