Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I think the success of the Mac is mostly a matter of marketing. Whatever your own personal beliefs, though, there's no denying that there are certain things Linux clearly does better than Mac OS X. If you're trying to decide on a platform for your business, these factors are worth keeping in mind.
The Mac might enjoy a smaller installed base than Windows does, meaning there's less of the monoculture effect and less of a lure for malicious hackers, but Linux blows them both away when it comes to security.
First is the question of permissions: Linux users are not automatically given administrator privileges on their computers, meaning that viruses and malware don't automatically have access to everything in the proverbial "castle." So, when a computer is compromised, the most the malware can typically do is trash the user's local files and programs.
With Apple, on the other hand--as with Windows--social engineering is painfully easy. Just convince the user to click on something, and away you go, with the castle keys in hand.
With Linux, on the other hand, there is a world of users examining the code every day. No wonder, then, that Linux vulnerabilities can be found and fixed more quickly.