4) Get users to download this ('free photoshop!' - see OSX/iWorm for an example of Mac user's being dumb) *or* inject this into internet downloads if you have network-level presence. Tons of OS X software is distributed over HTTP :/
so, again, like every other OS X exploit, this depends solely on Social Networking to propagate.
So, IOW, after about 100 or so Macs worldwide get infected, whatever package was responsible for spreading malware via this method would be added to Apple's malware list, be pushed out automatically to all users of OS X, and, like those infrequent times before, that would be that...
Then, Apple simply adds checking of DyLibs and other add-ons to OS X, and closes this hokey forever. Problem solved!
So, thanks to the black hat who brought this exploit to Apple's attention; so that they can take care of it.