When you friend request a person on facebook who you dont know at all or very well and they bring up your facebook request in person and say they dont know you in front of people, making you look like a weirdo.
Blake turned out to be a total facebook regret. He made me look like a creeper in front of everybody, when all I did was friend request him to be friendly.
Commenting or posting on a friend's wall and immediately regretting the action, in fear that they won't appreciate or enjoy the post, so much so that you consider instantly deleting the post rather than suffering awkwardness.
Two hours after posting the video with no comments or likes, Connie immediately was hit with a case of facebook regret.