Do you to point out their mistakes to others?

Do you know someone who thinks it necessary to report everyone's mistakes to them, to correct them every time it happens? Sometimes it can be difficult to keep it to ourselves,especially when we think we know a better way, but we should all try,unless someone's life or safety depends on it. I'm not saying it can't be done sometimes,or that we shouldn't help someone who is just learning a new job but I'm sure we would not welcome someone else pointing out our every misstep so why do it to others? Do you think that some people see it as their duty in life to make sure that all goes the way they think it should?