Early on, I thought that the "changes you will like" were going to run off a chunk of United's VFF/HVF, and that United was under-estimating the ripple effect from having to replace one reliable 25-75 trip/year or more customer, with 25-75 new customers buying on price, multiplied by 10 or 20 or 40 thousand customers. You might have to give up some potential "ancillary revenue" to keep that FF loyal, but at the margins they were going to choose United and they were at times, going to pay a little more or go out of their way to book United, or organize that out of town meeting in a way that would favor United for the booking, and so on. And sometimes, they were also going to influence a less well traveled traveling companion, or the family, or an entire organization. Each FF lost, is now going out of their way and giving up a few dollars on the ticket now and then to book Delta or AA or some other airline instead. And they are not going back without some sugar that will be more expensive than what United was paying before to keep them.

I don't think it is a coincidence that United's performance relative to peers has tanked while ancillary revenue has boomed.