"Yet there has not been one self replicating virus on OS X since its inception in 2001."
Does there need to be? Virus code no longer gets into computers to scramble your harddisc or display obscure political messages. It is looking to steal data. Login details, anything that can eventually be "monetized".
Okay, granted, in many cases the OS X trojans and stuff need to be given authorisation, but how many people tend to dismiss messages without really reading them? It is easy to not be vigilant, and it is even easier when stupid people say OS X is virus free. Sure, they may only be trojans, but they can hook into other programs (which is a replication of sorts), modify application data (including /apps programs), make merry havoc with instant messaging, and rip off data.
And that, my friend, is my definition of a successful attack. Not whether or not it has self-replicated, but whether or not data has been compromised. And using my definition, OS X is *not* as secure as you'd like us to believe. Oh, yeah, it is streets ahead of Windows, but not 100%. Nothing is.
For your reading pleasure, here's a link: http://www.sophos.com/security/analyses/viruses-and-spyware/osxhovdya.html and Google will find a number of others. I can't tell you if there are tens or hundreds or more for OS X because, hey, it's 4.30am and I actually don't care. But I found one compromise vector. In time, others will come. Perhaps ones of the sort where you, end user, don't have to do anything in order to get pwned.
So don't brag about never having a virus. Not having a virus is not the same as not being ABLE to have a virus.