Heck I used to see waaay more cracking of Unix back in the early 90's than Windows. I believe that it was because of the personalities, tools and education of the Unix folk then. When the tools for Windows cracking became mainstream, the "Kiddy Crackers" became the norm and sheer numbers drove them to the Windows OS.

No OS is safe. I run Linux, Solaris and XP64 at home, XP32 for work. Loads of advantages and disadvantages to each. Mac seems nice, but I don't like being tied to HW. The lesson is that nobody should be smug about security - everything can and will be cracked.