And whats to stop someone just closing their negative balance account I might add!
Probably nothing - but if their systems are sophisticated enough it might affect you ability to ever have a FF account with the same airline again (without having to deal with a negative starting balance, anyway). All just speculation, of course.
Citi will definitely claw back on the right issue. In my case, I had one of the original Signature cards and for some reason was overlooked when caps were introduced. I went a few years on this earning well over and then got lazy in transferring the points out.
It cost me from memory around 400K in points slightly lessened after complaining of the retro (something along the lines of putting up with the Gov't is one thing, but not when I have a choice) getting the Select for no extra on the first year.
Ouch, that really sucks. Did they notice the error on their own? Any talk to trying to claw back points you'd already transferred out to airlines?