Guys, this was END ON END, not back to back. This is legit. I have no problem with going after back-to-backs, because that cuts into revenue at no cost to the passenger (the cost being travel time).
Details -- I needed to fly AVL to LGA with no Saturday night stay. AVL to anywhere is expensive, especially with no Saturday night stay, so I found the cheapest fare out of AVL that will take me someplace that is cheap to LGA (unless LGA was the cheapest, which it isn't).
AVL-CAK was about $200 or $300 less than AVL-LGA, and CAK-LGA was the AirTran $79 match.
Most people won't do this, because it takes longer (see "travel must be via the fare combination point" in the fare rules). However, I like flying, so I welcomed the end-on-end opportunity.
What's interesting is that if US had value-priced AVL-LGA all by themselves rather than just matching discount carriers, I would have bought the cheap AVL-LGA and paid less. So, at least in this case, value pricing would have decreased revenue for US.