http://www.infobarrel.com/Secure_Delete_Files_on_Your_Mac
published June 1, 2009
Secure Delete Files on Your Mac
by mswengel
For security reasons, there are some files you don't want to be recovered. Fortunately, Mac OS X makes it easy to securely erase files.
You may want to securely erase files if you are dealing with sensitive financial data, personal information, and the like.