Facebook quizzes, polls, and trivia games are fun to take, but some are schemes to steal your profile, hack your identity, or just send spam.
Suppose you see a quiz about family origins. So, what is your mother's maiden name? The app will reveal all! But… didn't you just use that info as a bank security question? If so, you just gave unknown people access to the answer, along with all of the info on your Facebook profiles and page.
One notoriously evil app that did this asked for the names of concerts people attended — another common security question.
Pet names, birth places, best friends, first car, first teacher, vacation destinations–you are revealing answers you may have given for security or may give in the future. You'll forget about the quiz, but the quiz makers are never going to forget YOU.