Not necessarily. You can reformat your drive or use utilities to scrub empty areas of your drive. The mac now has what it calls Secure Empty Trash which scrubs the area the files were on.

There are programs that totally delete files with 6 or more overwrites. I got one called Incinerator that came with a suite of system tools but there are others. Here are some leads: http://www.google.com/search?hl=en&q...files+military