Visiting my sister, I noticed that all their icons had disappeared from the dock on their iMac. I asked what had happened, and my brother-in-law said, “That Mac is just strange!”
After thinking about it for a bit I figured it out: one of my sister’s children drags the icons off the dock because of the very cool poof-of-smoke sound and animation. Ha!
Since he just giggled when I asked him to stop doing it, I figured I needed a way to actually lock the dock. It turns out that this is possible with OS X’s parental controls, BUT you can’t apply parental controls to the admin account. And of course, switching between users being what it is in OS X, creating an another account wasn’t likely to work for my sister’s family.
So I found a useful piece of software called SuperDocker by Ed Shiro that has a simple checkbox to lock the dock. Works perfectly!