I heartily concur with Premex on this one.
Despite whatever waiver the airlines put on their elite program rules and changes, when an airline has a frequent flyer program that makes promises - both specifically by listing them in their program literature and tacitly by having the benefit levels and frequencies exist - and a passenger acts in reliance upon those promises - spending thousands of dollars over many months to achieve those promised benefits - there is an implied contract that those benefits will be delivered. When a passenger is at a point AFTER the time and money has been invested to achieve a designated mileage or segment target, and the airline changes and/or reduces the benefits, a fraud has been perpetrated upon the passenger.
The DOT and the DOJ should require airlines to make and set their Frequent Flyer policies in stone during the year in which passengers qualify for them, forbidding "bait and switch" practices, and forcing the industry to make future changes with sufficient advance notice so that passengers will not be deceived into spending even one dollar for a benefit that the airlines intend to or decide to remove.
This IMHO, as a class action suit, would be easily won. Sadly though, the only winners would be the lawyers.