So, if you're already involved with someone, you should probably be very careful how you use it. Whatever you do or say on it could easily get passed around your Facebook "friends" and get back to someone close to you in real life, potentially causing them grief.
However, this aspect of having so many people knowing so much about you via direct and indirect online contacts could also be a bonus for people who are single, and hoping to meet others like them. Which is why it's not surprising that a new dating site is combining several of Facebook's characteristics into its own structure.
As this article states, "the idea behind this site is that everyone on it shares their single friends".