Save the extra keystrokes required to launch your copy of Pretty Good Privacy for truly sensitive data. There are clearly times when encryption is a must. Such as protecting data that is potentially embarrassing or financially valuable. Your boss can easily browse through office e-mail. Online services, such as America Online, regularly maintain copies of your electronic missives.
Schools also can gain access to correspondence in their systems.
If in doubt, encrypt it. But encryption is not an easy process. To work with an encrypted file, you first have to unscramble it. Then when you're through editing, it has to be re-encrypted. Finally you have to delete the plain text that the decryption created.