I was watching Arkansas/Georgia, and there was a play where the Arkansas receiver was tackled on the one thanks to a facemask. The personal foul was called, and the penalty for a pretty blatant infraction was half the distance.
That doesn't seem right to me. I think a personal foul should always result in a more severe penalty than something like holding or offsides, but that's not the case as you get close to the goal line. I don't think you should give a team a touchdown in such a scenario, but there should something more than 18 inches. Maybe an extra down.