The carriers take this ever more seriously both because there are large amounts of money at stake and because the technology is so much more sophisticated and picks this fraud up much more readily.

Fares are on a market-based system of supply & demand. That's why it costs more to fly AAA-CLE than AAA-CLE-BBB. The carrier is selling you an itinerary from AAA-BBB which happens to involve a plane change at CLE.

GA and other customer-facing personnel have heard every story in the book. Somewhere there really is some poor slob who fell and broke his leg running between two flights and then couldn't fly the second segment, but that's a rarity.

The "tell" is when the pax misses the outbound connection and then doesn't want to be rebooked on a later flight or is rebooked and then misses that too.