Not everyone has the same level of experience and training with computers so there are going to be lots of differences in opinion and some unintentional mistakes made. To mildly misquote a wise person "never attribute to malice (or fanboyism) what is adequately explained by ignorance".

It is possible to write malicious software for any computer system / operating system. Having said that, the basic architecture of Windows (at least thru XP) is much more vulnerable to true Viruses or worms when compared to Linux, UNIX and OS-X.

MS Windows is a much more target rich environment (more common and therefore more targets and more badguys) but the other platforms are not ignored - there are lots of attempts to show how "vulnerable" Linux and OS-X are but to date the worst the various teams have managed are some demo's that might work under very controlled conditions. I am pretty sure there are no current Apple or Linux specific exploits "in the wild" that are equivalent to the worms and viruses currently impacting a lot of PCs. To someone who is a more casual user that surely looks like "there are no mac viruses".

I am always at a bit of a loss when people bring up Anti-virus SW for the mac as indicating that Apples must have viruses. Most of these companies are out to make a buck not help the users. Many of the "viruses" they scan for haven't been a threat to the Mac in a long time (as in no longer matter with the current OS) assuming they ever were a realistic threat. The other things they seem to scan for are application vulnerabilities (like Flash, or Adobe acrobat reader) which are not exactly Apples responsibility. This is also where some of the architectural choices behind OS-X are better at limiting the impact of the malware than the same exploit on Windows.

In many cases the recent "viruses" aren't really true viruses but require a social exploit also - having the user do something specific to catch and share the "fun". In my experience those who fall for these things will continue to do so and there is very little I or the OS designers can do to help these people. Currently this is mostly Windows users (due to population size) but I expect we will see more of this on other platforms as they grow in popularity.

- Eric