There was ONE person who decorated their windows using glass markers that was told she would be charged if she didn't remove it........but that was several months ago, and no one has had a repeat of that threat. It's widely believed that the only reason she was singled out was because of the markers used on the windows. I'm sure from mousekeepings point of view those would be a wicked mess to remove!
We were there from November 16 to December 14, 2008, in three different resorts, and had our windows FULL of things that we received from the wonderful DISigners on this board. We changed the "theme" on our windows daily. We received compliments from the mousekeeping folks in each of the resorts, and actually had our mousekeeper at POR pose for a photo with my girls in front of the window (we took a picture of the girls every day with the new window decor). We also had other guests taking photos of our windows, lol....now THAT was quite a kick.
We also had magnets on our doors at POP and at CBR....we couldn't get them to stay on the doors at POR for some reason, so after finding them on the ground the first two days we took them down.