What is the worst case of "You think you're helping but you're not" you have ever experienced with a stranger?

Have you ever gone out of your way to inconvenience someone who deserved it? How did it play out?
Have you ever kept a secret that could have affected multiple people if revealed? What made you decide to keep it quiet?
Are we underestimating how quickly AI will change ordinary businesses?
What's the psychology behind supporting a political figure despite acknowledging their failures?