You really must try to be this ignorant because even noobs can understand this. He gave an analogy of why a Mac virus wouldn't spread easily in the wild. So the first has already happened. A couple times but it keeps getting dismissed. Remember we spoke about 1 year ago on the exploit available in the initial release of OSX. Yes it was patched but if you install osX without patching you would be vulnerable out of the box. Now with MOAB #1 we have again proof that osX is exploitable, but the mac faithful keep downplaying it and obfuscating the issue. They can do this by saying it's not in the wild. Reason it's not in the wild is as crusher detailed...there aren't enough machines to spread it properly.
Remember just because it isn't in the wild doesn't mean it can't exist. An exploitable hole is an exploitable hole.
Name one. The two you named are dismissed because they have never spread in the wild, only under lab conditions with engineers trying to get it to spread.
Reason it's not in the wild is as crusher detailed...there aren't enough machines to spread it properly.
You also seem to like percentages. How about hard numbers. There are over 25 million OS X boxes out there not getting infected. The sadmind worm spread widely through Solaris 7, and I think we all agree there weren't even close to 25 million unpatched Solaris 7 boxes out there (Sun had issued a fix two years before). The IIS component of sadmind is irrelevant, since it only modified web content, not using IIS as a vector.
There have been propagating virus/worms for devices with a far smaller installed base, and you don't think OS X with 25 million installs has a critical mass? Rubbish.