Yes, it can definately happen, even if you book a higher category. We had friends who had booked connecting category 6's and were upgraded to connecting cagetory 4's. You'd think they would have been estatic!! Well, the 4's were VERY forward in the ship (they're 6's were mid-ship) and they had severe motion problems from being so far foward. They weren't happy at ALL. I've also read several reports of people who booked a certain category only to be moved to an undesirable location, though an upgraded category. I would be upset too. We booked a guarantee category 6 and NEVER will book guarantee again. We got 6556, which you think would ge a good room, midship and non-connecting. WELL, the room was SO LOUD I couldn't sleep. The entire room vibrated and during the day it sounded like hammering in the floor beneath us. After several calls to Guest Services they told us it was the high pressure water line they use to clean the decks ran underneath this cabin. Whenever they turned it on, usually at 3AM, our entire cabin would vibrate and you'd hear terrible noise. This also happened during the day too. We kept voicing our displeasure and eventually were moved to 8092, an upgrade to a 4. Now, this was almost as far aft as you can get and had a solid veranda, which was a bummer for our kids. But, we LOVE aft and took it to get rid of the noise. This location was quiet, with the exception of the connecting door and the kids next door who always slammed the door when coming/going.