There are many things to consider when organizing contests or sweepstakes. There are the country or region specific legal things to think of and there are the Facebook rules as well.
Because breaking the law may result in very bad things to you like paying a penalty. And because if you forget about the Facebook rules you might end up having your Facebook page (the one you just wanted to promote) closed down.
- acknowledge that the promotion is in no way sponsored, endorsed or administered by, or associated with, Facebook.
- mention in your texts that the participant is providing information to you and not to Facebook.