A virus really isn't a problem on a platform where you can just reinstall the system software by unplugging the battery...
Besides, if you get one, just plug it into activesync, and delete the malicious file manually. There aren't many files, so it wouldn't be hard to find.
*nix could definitely get viruses, but the main reasons why it rarely does are:
a
) binary programs cannot just execute themselves unless if you spectifically make a root script to do so, and to run a program in a directory, you have to type sh before running it, or ./ so that *nix knows to run THAT program, and not the one in /usr/bin, etc. So by typing a system program, you will not run the possibly malicious one in the directory you are in, you would have to run the virus on purpose.
And
b
) Unless if you are crazy, you do not do your normal work as root, but as a user. So if you execute a virus, it only looks for and infects binaries in your home folder, which you should not have anyways, as they are all in the root folders. So the virus would just die. You also could not make a script to automatically run a program without being as root anyways, so a virus really would not have a chance to DO anything, unless if the system administrator is...dumb
So there you have it, why viruses do not happen often on *nix systems. Common sense.
