By my calculations, my favorite reward (one week at a category 6 hotel) now costs 180,000 points when it previously cost 130,000 points. Yes, I know this is less than the old "stay anytime" rate of 260,000 but I never used the stay anytime rate. By planning ahead, I was always able to use the 130,000 point award. My calculator tells me this is a 38.4% increase.
My existing points have just been significantly devalued. I saved up 390,000 points for an upcoming trip involving three category six rooms for a week. Now my 390,000 points will get me two rooms plus one room for one night. Ouch. Yes, I know Marriott has the right to make these changes. They also have a right to lose customers if they wish. Ask any intro marketing student if they think this change will add or detract brand value and customer loyalty for the company. The answer is pretty clear. An alternative? Give existing customers who have saved points a more reasonable amount of notice so they have a chance to use their points under the terms in force when they earned their points.