As their rules tell us, the program can pretty much change how it wants. It is up to the customers to adapt.

I've been Diamond for a while now, and it is pretty clear to me that with the recent changes one of the primary benefits of Diamond status is now available for even fewer stays per year.

This is fine, and will certainly affect customer behavior. There is less incentive to go for Diamond under this program, since Gold is adequate. Since my travel does not decrease, the previous business given to HHonors to bridge the gap between Gold & Diamond will now go to another program- most likely Marriott's. I will be happy with HHonors Gold now.

This is not a retaliation by any means. It is just business. There are no hard feelings, but this is the behavior that is being rewarded by these changes.

Now that I think of it, some day this sort of change, added to the confusion around the Rolling Tier program, and the recent 5-10-15 offer where one set of responders was immediately rewarded, with the other set being continually ignored, could well be the subject of a B-school study.