I inadvertantly flew without an id a few days ago.

I had bought a AUS-DFW ticket on AA

Then I had a DFW-DTW ticket on NWA...I printed this boarding pass on-line.

Since I was inside security, no one ever asked to see an ID from DFW-DTW. I could have used someone elses ticket.

An interesting trick since you normally cannot change names to ticketed reservations, but your are not asked for ids once you are inside security.

I guess, you could also buy a refundable ticket to just get inside security and then do something similar.