The Consumerist has a thread on flying without ID. Unfortunately, their answer isn't very helpful--basically they advise that even though ID isn't necessary--run out GET ID as soon as possible anyway. Some of the commenters share interesting experiences about flying without ID. Unfortunately, the experiences described don't have any date information, so they won't be posted here directly. There is one particularly relevant post TSA deferred to Delta airlines on deciding about ID. This seems recent because TSA was in fact checking the IDs at the time, and let the passenger fly as a selectee on the originating flight. This is disturbing because it suggests that TSA is enforcing corporate policies, rather than the law (secret or not). The Delta rep also threatens that the flyer will be put on a list:
At the sceurity screening in Charlottesville, Virginia, I realized that I'd left my driver's license at home. "No problem," said the kindly TSA ID-checker. "You can travel without a driver's license. You'll just be a selectee."
With that he wrote "SSS" on my boarding pass, and when I went through I was taken aside for the extra-special treatment: full wanding, luggage dump, jokes about having to confiscate my doughnut.
They couldn't have been nicer.
On the way back, however, in Dallas, the TSA ID-checker sent me to the Delta counter, where the Delta representative told me that I couldn't possibly fly without an ID. "I don't care what they told you in Charlottesville. Looks like you'll be taking the bus home."
Eventually, an even nastier Delta supervisor decided to let me travel. "But you'll be on a list from now on." He wouldn't tell me what kind of list, and I decided not to press my luck.
Curiously, the authority that made the decision as to whether or not I could fly apeared to rest with the Delta supervisor, and not the TSA screeners.