He said in his reply (and I wish I could find it) that POSIX compliance was a big deal for OS X, and part of the reason why so much of the FreeBSD userland was being used (I was also involved in some parts of FreeBSD at the time - there was a whole initiative around making it fully Posix compliant, way before any other free UNIX).
I knew some of the history with Next and POSIX, your comment tied the story together for me. It does show that Jobs learned his lesson when he went back to Apple.
Now more on the topic at hand. Apple need to handle security issues better. Not just in terms of disclosure but in response times and communication with the industry. You don't see many/any Apple reps at the major conferences, and no engagement at all. It was always generally known within the industry that Apple owed much of its OS X security to the fact that it just wasn't a big target. The commercial UNIX releases and Linux were targetted because they ran the worlds servers, and Windows was targeted because it was the worlds desktop. Now with OS X gaining market share they are getting more attention from sec experts and hackers.
Microsoft reformed their security policies back in 2000, after IIS 4 had a horrible run and the code red worm ran wild. Many top security and secure coding experts went to work at Microsoft at the time - it was a major shift (implementing security checks in every step of the dev process across the whole company). Apple have only had to do this more recently, and they haven't really perfected it.