There's nothing to gain from saying it to a coworker. You should: - Remind them next time it's relevant - "Remember last time we touched this service and the W

There's nothing to gain from saying it to a coworker. You should: - Remind them next time it's relevant - "Remember last time we touched this service and the Widget crashed and took the rest of switch down with it? I think this could be similar and we should reconsider my plan to isolate the network before hand." - Mention it to your manager. Failing to heed a warning can be blameless and rational, but if you're consistently right when others aren't that's a sign you should have more formal influence (and responsibility). You won't get that by complaining to peers. - If it was extremely serious (it rarely is - the really bad stuff is usually stuff no one foresaw) and your concerns dismissed out-of-hand (also rarely the case - people legitimately have different priorities), discuss it with your/their manager. You can also of course do it if there is no other escalation path - CEOs and EMs ideally didn't get where they are by being unable to take criticism - but you should also be very sure your advice really was right, and not a stopped clock.