I do not think Apple is interested in market share past a certain point. I think they are happy enough hovering between 7-9 percent market share in computers. Besides, they dominate the portable digital audio player market (iPod) and are highly competitive in the smart phone wars. Like em or not, they have built a marketing machine that works.
I believe what Tindytim was referring to is/was a weakness in Safari which was not found on the first day of competition, but was exploited the second day when direct network access was permitted. And the winner Charlie Miller, had admitted having previous knowledge of the weakness. So doing it in the time he did it in, not really an indicator of platform security. Windows Vista Ultimate SP1 also fell to the wayside, leaving only Ubuntu 7.10. That aside, OS X is based on BSD and Unix (which the "all secure, all knowing" Linux is based on), which are generally considered to be two of the more secure platforms by many security professionals.(http://techupdate.zdnet.com/techupdate/stories/main/0,14179,2822483,00.html) BSD being at the top of that list for servers. So, I'm not sure Apple would have all the same issues or more that Microsoft has had. Many of Microsoft's have come from poor design and bad programming, because they are a relatively young OS, when compared with Unix and some others. But to say that because Apple WOULD have many more because they aren't tested as often (I assume Tindytim means there are fewer of them, so they are not as glaring of a target) is not necessarily correct, and in not a valid conclusion. However, on the flip side, he may be right. But I am led not to agree given the platform base which OS X stands on, and is built upon.