It isn't misused every time. Quite the contrary - it's a critical part of HN's immune system. Without it the site would be taken over by pathogens.

We don't have anything close to the mods we would need to examine every HN post, so relying on the community is a must, and the vast majority of users who flag posts are doing it responsibly.

This system doesn't always work correctly. If you see a post that shouldn't be flagged, let us know at hn@ycombinator.com. We often turn the flags off in such cases.