First impressions stick for a while, but when they wear off and you discover you were wrong about a person, do you regret the way you acted towards him/her at first? Might you even admit to being embarrassed about it?
For example, upon first meeting someone, you find that you really like them. You're both kind and polite towards one another. Over time you learn more about them and from this you decide you don't really like them. Are you ashamed of thinking they were okay to begin with? Are you afraid of what people who have always felt the same way about this person might say? Or do you just brush it off and admit to being fooled in a way?
Or maybe it's vice versa. Maybe you really don't like a person at first, and you don't treat one another nicely, and then somehow you end up becoming great friends.
Either way, I think some degree of awkwardness would exist for a bit. How would you feel? Has this ever happened to you?