FaRmLaNd on 22 May 2009
Lack of marketshare and unix heritage.
All systems have virus's just some aren't worth it to target en mass as hackers would want to affect as many people as possible.
I've been running my mac for 3 years now and I haven't had a single issue with virus's or security. Although I admit I wouldn't have significant troubles with any system because I'm careful. However the lack of virus's is one of the best things about osx.
