I apologize if someone has addressed this issue between posting and this reply, but TSA is all about Kabuki security theater to impress Ma and Pa Kettle, at the gates, who fly every other year. Given that background, using military personnel to staff TSA would be a brilliant PR move to impress the sheeple at gates. However, in terms of actual security, using military personnel at gates would be a disaster.

We know from efforts in Afghanistan and Iraq that ordinary military units are not geared toward engendering favorable PR with those it encounters. As others have noted above, the purpose of the U.S. military rightly so is not to sing "Kumbayah", but rather to kill enemies and to destroy things. Current TSA employees have exhibited a concerning streak about treating American travelers as enemies, guilty until proven innocent. Based on training and purposes of the Army, and for that matter the Marines, one would think that ordinary military units would be even more inclined to treat ordinary Americans more like criminals than like travelers.