IT is the Facebook app that was never going to struggle to find a user base.
Titled "Bang With Friends", the app allows people to anonymously register interest in sleeping with their contacts.
If their interest is unrequited, it remains a secret. If the other party has also ticked the box to register their interest, then they are both made aware.
More than 20,000 users have signed up in just four days.
"We're just giving you closer access to the truth," say the app's California-based creators.