This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
Eric is exactly right. Even if you have client-side guards to prevent this, you still need code not he server to detect and prevent this condition as you can never be certain that the client-side guards will be used.