How/Why did the Fairfield Inn & Suites Cleveland (Tennessee) go from a Category 2 (10,000 redemption points) in December 2011 to a Category 3 (15000 redemption points) in May 2012?
Welcome to the Marriott Insiders site. Category changes were announced on this site in March. I believe that I am correct in saying that the number of night stayed using points is what causes the category to change.
Here's the list of category changes 2012 Marriott Rewards Hotel Category Changes List and the announcement itself Marriott Rewards 2012 Hotel Category Changes