I have a whole differente view on this than the one i'm getting from most of the posts.
Hacking and writting virii makes computer systems better, indirectly of course. When a hacker breaks in to a network it's network admin racks his head trying to figure out how he/she got in a to prevent it from happening again. The some goes for virii, but big companies like Microsoft don't seem to be as diligent as the regular sysadmin, unfortunately.
Now i know this fact in no way excuses these actions for they are in too many cases done with malicious intent. But they in themselves are not malicious.
I believe that computer systems need to be constantly attacked to keep up their strength. I don't believe it should be done strangers with malicious intent, though.
If a company hires someone to attack their system and work with the sysadmin to make it stronger, i think nothing would be better.
Now the same doesn't apply to Anti-Virus software for a simple reason: those companies profit from existance of virii. The companies that should take advantage of the virii to improve their products are, basically, the OS companies (ie: Microsoft).
I've heard, i don't know if its true since i've never worked in that enviroment, that Linux is pretty much inmune to virii, is that so?
Oh well, just my 2cents.