I think given the dual purpose of requiring ID for travel, it would be very difficult to travel anomomously on any common carrier. For security purposes, requiring ID is nonsensical - it offers nothing to improve security.

However, the airlines (and other common carriers who issue tickets) have always had a vested interest in knowing who their customer is. In the past, given no competitive impetus to do so, airlines just assumed the person showing up to fly was the same person whose name was on the ticket. Way back when, before deregulation and restricted tickets, it probably didn't matter much either.

With restricted tickets barring transferability, the government gave the airlines exactly what they wanted - the right to demand ID to make sure the person traveling was the person named on the ticket. I doubt the airlines really believed this was for security...it was a revenue protection gift all along, even if the government really believed it would provide security.

In the past, ID was checked at the counter. With the advent of online check-in and kiosks, the responsibility to verify ID now falls to the ID checker positioned outside the screening area. This opens up a unique way to bypass the revenue protection requirement.

I can transfer a ticket to another person by having that person buy a refundable one-way ticket to get through security, I use online check-in to get their boarding passes for my ticket, then they use my ticket for passage. Upon their return, they just cancel the refundable ticket(s). Voila. Revenue protection is now bypassed.

Just proof positive that every new rule has its own loophole.