Well, I had my first experience with one of those "vanishing" colonies today. I'm not going to call it CCD because I haven't opened this hive in several weeks and don't know what happened or when it happened. All I know is that I went to check it out today and knew something was wrong before I even got to it. The two beside it were quite active. This one was dead quiet. I popped the top and the top box was empty. No brood, honey, bees, nothing. Pulled that box off and the next two were the same, other than a few robber bees and a wax moth. These combs were COMPLETELY empty, other than a little bit of pollen. No dead brood or anything. No dead bees on the bottom board or the ground around the hive. I have no idea what happened. Luckily, I got to it before the wax moths had time to do any damage. I threw all of the combs in the freezer.
This was a 2013 queen. All that I can figure is that she croaked, they failed to make another, and the remaining bees left. Maybe they went into one of the other hives.