Secret Crush is a feature of the Facebook dating service that helps you find out if secret crushes like you back. Once you've joined Dating on Facebook, you'll be able to create a list of up to nine Facebook friends that you're interested in. If they also join Dating on Facebook, they'll be notified that they have a secret crush. If they also create a Secret Crush list and put you on it, Facebook will let both of you know that you've matched.