"Tragedy of the Commons" comes to mind. It describes the behavior of people when there is a scarce public resource. People will tend to use as much of the resource as they can because they are afraid others will get to it first. This behavior quickly depletes the resource contrary to the public good.
WikipediaWikipedia has a concise definition:
"The tragedy of the commons is an economic theory of a situation within a shared-resource system where individual users acting independently according to their own self-interest behave contrary to the common good of all users by depleting or spoiling that resource through their collective action."
