Why do you think that the helpful drivers that kept us coming up in IBSS mode (proper name for new "ad-hoc" mode) won't use the keys as well?
Ok, I didn't know that.
Further, as was said, it does nothing against malicious rogue APs?
Rogue malicious wily ruthless users skilled enough to configure hostap can rightfully be blamed; but not the novice user turning on a particular vendor's laptop.
Alex