I'm curious as to how that would violate the fare rule if the all of the itineraries were priced out for the same fare class. As far as I'm aware, there's nothing that states that a person "has" to complete a trip. If I were moving to a new city and the roundtrip airfare was significantly less than the one-way fare, I'm going to purchase the roundtrip fare and only use the first leg. Why should the airlines care if I decide not to return on the second part of the ticket? I know they factor in the loads for each flight based on the tickets purchased, but they also factor in for the number of "no-shows".

As far as repercussions, what would the airlines do, assuming they do monitor who does not complete a full itinerary? Are they going to say, "Sorry Mr./Ms FFlyer, you never finished your last trip so your not going to be able to fly with us again until you do. It doesn't matter that you've purchased another full ticket."? If this was the response, I know I would start flying with another carrier (100,000+ miles/yr).

Instead of forcing people to "play the game" in order to get a decent fare, airlines should look into why people are playing the system in the first place. In the example I used, the DTW-FLL-DTW flights were EXACTLY the same whether I started at DTW or in FNT. The only difference was my starting point and, for me, that was only a minor change since the distance between the two airports is the same. If anything, I would have expected it to be cheaper if the first leg (FNT-DTW) was eliminated.