Taking this idea of UL travel a bit further, I spent most of Monday at various airports traveling from SFO, to Phoenix, then LA, and back to SFO. But what made the trip considerably more of an adventure than usual was that I was flying ultra-light.
I'd left my wallet at home. I had no ID at all: no drivers' license, no business cards, no credit cards, nothing at all.
Which is how I found out that it is, indeed, possible to fly without a photo ID. They ask a lot of questions, and discuss it all with NTSA in Washington DC...but once they are satisfied that you are who you say you are, they let you fly.
And since each airport has a slightly different protocol, I was able to verify this three times in one day.
Not exactly the way I had planned it, and not something I would recommend. But it is posslble.