I great idea in theory. As you can obtain miles, or have an alibi if you murder someone, etc. HAHA
However, the plan fails if your flight is detoured or emergency situation and everyone needs to recheck into security area. While this is infrequent it can happen with summer storms, mechanical difficulties, etc. so your flight from DFW to ORD is landing in ST. Louis and must show ID to check in to different aircraft.