If one assumes for the moment that an individual or a group is planning to commit another 9/11-style hijacking operation; and, if you assume that these individuals have a high degree of probability of being on somebody's "list" or at least being flagged for SSSS, then it would make sense for this group to either fabricate a benign identity or steal someone else's identity.

Simply stealing an identity is an almost trivial act if you remember that stealing an identity to buy a plane ticket without drawing attention to yourself is a short-term proposition. Once, I had a credit card stolen or I dropped it and someone picked it up and started using it. I reported it less than 12 hours later as soon as I discovered it was missing. That was enough time for the thief to drive 100 miles away and charge about $500 of merchandise at several different stores.

In terms of getting through an airport checkpoint, all someone would have to do is to buy a plane ticket -- round trip -- using my credit card and make up a fake picture ID using my name and their own picture. All of this could be done before any system -- particularly one involving one of the famous "lists" -- flagged the credit card as stolen. Heck, if you do it within 24 hours of the flight you intend to hijack, you could go to a Kinko's and print out the boarding pass before the credit card was even reported stolen. I'm not sure that a stolen credit card would even set off the bells & whistles on one of the "lists" anyway. This would give a fake ID printing team plenty of time to make up something good enough to get through the checkpoint. The ID checkers -- including the intrepid TSA moat dragon -- only check names on the picture ID and the boarding pass. None of this discussion of establishing a track record even matters if you steal a credit card tied to an individual with a "track record" and use it right away to buy a ticket and print a boarding pass.

This scenario, because of the "last-minute purchase" component, might cause the bad guy(s) to be SSSS'd. But, if their plan calls for them to take control of the aircraft (or blow it up or whatever the objective is) without taking any prohibited items through the checkpoint (exactly what happened on 9/11), who cares if they're SSSS'd or randomly secondaried? The worst that will happen is that you'll get groped and yet another TSA officer will compare the name on the boarding pass with that on the fake ID.

Post 9/11 security is just like my home security system. The best I can hope to do is to defeat or deter the amateurs. The "professionals" can defeat either system with one hand tied behind their backs. So, if one is trying to explain why 9/11 hasn't happened again, the much-expanded and very expensive ID check system -- present and future -- is certainly not a good reason.