We’ve all been warned to beware of unintended consequences. It’s so easy to do something, or not do something, without thinking through the consequences of our actions.

But if we’re not careful, we may bring about a result we don’t want. In fact, if we’re not careful, sometimes our effort to prevent an outcome will actually promote it.

Here are some memorable examples.

Pickpockets sometimes lurk around “Beware of Pickpockets” signs, because when passersby see those signs, they pat their pockets or check their purses to make sure that their possessions are still safe. In this way, they show pickpockets exactly where to find any valuables.

It turns out that the classic cornfield scarecrow attracts birds, because the birds learn that a scarecrow is a sign of ample food.

After an archeologist announced that he’d pay handsomely for each ancient well-preserved artifact, enterprising people broke artifacts into smaller pieces.

Beware of unintended consequences.

These stories are good reminders that we shouldn’t assume we can always predict the consequences of our action, and we should pay attention to what actually happens.