Not only are AV software running privileged services in the operating system, they're also full of security holes in themselves.

I seem to recall a talk at Black Hat, but I can't seem to find it now, where someone did some basic file format fuzzing and could reliably run code in almost all of the popular AV software.

That's scary. I would also target them if I was a black hat or a three letter agency (which basically amounts to the same in this context).