The risk the big airlines take with these devaluations is that Joe Sixpack the infrequent flyer realizes the value is dropping. Many of those trillions in unredeemed miles are in individual accounts that have been slowly building up for years. Imagine Joe has just under 20K, is excited about getting his first-ever award ticket, and just took a long-distance company switch on a 5,000-mile offer to try to top up. Then this hits. Could be a real turnoff, eh?

Maybe this straw won't break the camel's back, but at some point (especially if after repeated devaluations) the public could go sour. And that would cripple both the revenue from the non-flight mile selling and the perceived value of the programs themselves. Don't forget that the programs and promise of maybe a trip to Hawaii someday are some of the most potent weapons the big airlines have against the LCCs.

My guess is that if the big airlines do follow, we'll get a heaping helping of baloney about fuel prices or terror-related security costs or some other external factor being supposedly behind it. And most laymen would buy that, even though the consequences above would still apply. You certainly won't be hearing the airlines fessing up to the seat supply/unredeemed miles imbalance that they themselves created.