Right before they began to close up the walls in our house, I walked through the house with my Flip video camera and captured almost every wall in video. The 15 minute long clip with some incredibly dry commentary by yours truly is not going to the Cannes Film Festival anytime soon, but it has its uses. When the drywall installers come through and cover the walls, they occasionally forget to cut out and expose all of the electrical boxes and other important objects. In our case I can think of at least three items that were covered over. However, with the video (and a lot of digital photos taken by the contractor) we are able to easily see what is behind the walls and where.
In the riveting photo above, you can see the blue electrical box beside the drain for the master sink. This is for a small circulating pump that, when you press a button, cycles the water from the hot water pipe to the cold water pipe and allows you to get hot water to the tap without pouring a lot of water down the sink -- a great green feature. With the electrical box covered over and everyone's recollection of its location not so good, the video allowed us to find it. This was especially useful since the cabinet and tops were already in place.
It only takes a few minutes, and the file is not that big so I strongly recommend doing this for your home. It will also help later if we are looking at how something was run or making changes.