Add all your friends to Secret Crush. Watch who matched you.
"Sorry buddy, I wasn't really using the thing, I just added everyone, but thanks for letting me know you like me!"
Idiots. And this is why the shared identity is a terrible idea for dating sites. You want dating profiles to be throwaway, and you want it to be hard for your friends to find your dating persona for this reason!
But of course Facebook doesn't understand the need to keep secrets from (some of) your friends.