Speak Now Or Forever Hold Your Peace?

Imagine your single friend meets someone. You hear all about him for months. How sweet he is, how good looking he is, how chivalrous he is, how good he is to her, etc. etc. etc. And you get excited. Thrilled. This is a dream come true. And then you met him, and he's well, not someone you would go for, but it doesn't really matter, your friend seems pretty happy, so you don't say anything.

They keep dating. You keep refraining from saying anything. Things are starting to get serious. Your ealize that your friend doesn't really seem as happy as she was at the beginning, but he's doing all the right things in terms of being "marriageable" (which as a woman in your mid to late twenties, is a key priority) and so you still don't say anything about your concerns.

And then the day comes when you get that e-mail/phone call/text message.

"We're engaged!!!"

And then you realize you're screwed.

a) You're stuck with a man in your life that you loathe and or think is not good enough or right for your girlfriend

b) You realize your friend is stuck with a man that is not good enough or right for her. (WAY MORE IMPORTANT THAN A)

The question is: do you ever say anything? If your friend has gotten engaged to someone you perceive to be Mr. Wrong, do you speak, or do you forever hold your peace? When forever comes into play, is it better to be honest or politically correct?