Commenting on the state of OS X right now: There's this 'Gatekeeper' feature (which can be disabled, but starts enabled) that makes it so a developer has to have a signed certificate from apple in order to run on OS X. If someone starts releasing malware with a previously obtained certificate, Apple will send an update that disables that certificate.

I think that, once smaller developers start getting their apps signed (I'm not sure how hard it is to do this) then this will be a wonderful tool, and already probably is nice for non-power users. I currently leave it disabled because enough of the stuff I use isn't signed, but in the future it might be a nice step forwards for security.