Psychology students often hear that correlation does not equal causation. Given that this is true ...

Research has shown that the people often see a correlation between two events when one does not really exist. Why do you think this happens? Can you think of at least two situations in which this should not occur and at least two situations in which it is more likely to occur?

Psychology students often hear that correlation does not equal causation. Given that this is true, what are at least two ways in which knowing about a correlation between two variables/constructs can be helpful? How could knowing about a correlation between two variables lead to erroneous interpretations?