DoD has its own smartcard-based PKI, which is what those certs are tied into. Apple supported those smartcards natively with earlier versions of Mac OS X (though you had to install the root certs yourself) so it wouldn't surprise me at all that Apple is trying to make their gear "out of the box" compatible with DoD's PKI-based web services.

Not even necessarily so that you can use Mac in DoD, but so that a soldier, sailor, Marine, airman, etc. can buy a Mac for their own personal use and still login to those damn training sites, pay processing sites, etc.

After all, if DoD wanted to do nefarious things with a digitally-signed something or other, they'd just buy the digital cert needed from VeriSign or whatever today's equivalent of DigiNotar is, instead of something so hopelessly obvious.

But don't let me interrupt the jerk.