You can create a scarcity out of thin air as well. I was reading a trivia site the other day and it mentioned one incident like this in history. Apparently Johnny Carson made a joke on TV about how the States was running out of toilet paper. It was referring to a different situation and had nothing to do with the actual supplies of toilet paper.
But people thought it was a real problem and so they ran out to the supermarkets and stocked up on toilet paper. Which, of course, meant demand skyrocketed and caused an actual shortage of toilet paper, since they couldn't deliver it fast enough to keep it on the shelves.
I don't even want to say that people can be idiots, because really, they had no way to check whether it was pure humor or a cynical comment on something that was actually happening. And it happened!