[theGimp]

Good observation. If you're wrong, you suffer a brief moment of embarrassment. If you're right, you might prevent a disaster.

Speaking up is a no-brainer.

[bovitclan]

I don't mean to be a downer, but you could certainly cause an accident by calling out an observation which was faulty. I agree with the sentiment that you should speak up when you see something amiss, but let's not kid ourselves that, like every decision, it comes with inherent risk.

[mckoss]

Making an aircraft go-around can never cause an accident - the missed approach path for any landing aircraft is always kept clear.

[khazhoux]

I wonder how many people have died throughout history due to embarrassment, or (similarly) going against your instinct. The number exists but is unavailable to us.

- Not having that dark mole near your privates checked out.

- Not wanting to turn the car around.

- Not walking away when those shady guys walked in.

...

[avh02]

Korean airlines decades ago had a huge issue with copilots not speaking up to captains when concerned. While not embarrassment - there was a lack of speaking up. IIRC they forced cultural change in order to make it less of an issue.

edit: not speaking up