Facebook NOT ALLOW to have any contest, competition, sweepstakes or other sililar offering or promotion !

Promotions Guidelines
Date of Last Revision: May 11, 2011
These Promotion Guidelines, along with the Statement of Rights and Responsibilities, the Ad Guidelines, the Platform Policies and all other applicable Facebook policies, govern your communication about or administration of any contest, competition, sweepstakes or other similar offering (each, a "promotion") using Facebook.
If you use Facebook to communicate about or administer a promotion, you are responsible for the lawful operation of that promotion, including the official rules, offer terms and eligibility requirements (e.g., age and residency restrictions), and compliance with regulations governing the promotion and all prizes offered in connection with the promotion (e.g., registration and obtaining necessary regulatory approvals). Please note that compliance with these Guidelines does not constitute the lawfulness of a promotion. Promotions are subject to many regulations and if you are not certain that your promotion complies with applicable law, please consult with an expert.

1. Promotions on Facebook must be administered within Apps on Facebook.com, either on a Canvas Page or an app on a Page Tab.
   
2. Promotions on Facebook must include the following:
   a. A complete release of Facebook by each entrant or participant.
   b. Acknowledgment that the promotion is in no way sponsored, endorsed or administered by, or associated with, Facebook.
   c. Disclosure that the participant is providing information to [disclose recipient(s) of information] and not to Facebook.
   
3. You must not use Facebook features or functionality as a promotion’s registration or entry mechanism. For example, the act of liking a Page or checking in to a Place cannot automatically register or enter a promotion participant.
   
4. You must not condition registration or entry upon the user taking any action using any Facebook features or functionality other than liking a Page, checking in to a Place, or connecting to your app. For example, you must not condition registration or entry upon the user liking a Wall post, or commenting or uploading a photo on a Wall.
   
5. You must not use Facebook features or functionality, such as the Like button, as a voting mechanism for a promotion.
   
6. You must not notify winners through Facebook, such as through Facebook messages, chat, or posts on profiles or Pages.
   
7. You may not use Facebook’s name, trademarks, trade names, copyrights, or any other intellectual property in connection with a promotion or mention Facebook in the rules or materials relating to the promotion, except as needed to fulfill your obligations under Section 2.
   
8. Definitions:
   a. By “administration” we mean the operation of any element of the promotion, such as collecting entries, conducting a drawing, judging entries, or notifying winners.
   b. By “communication” we mean promoting, advertising or referencing a promotion in any way on Facebook, e.g., in ads, on a Page, or in a Wall post.
   c. By “contest” or “competition” we mean a promotion that includes a prize of monetary value and a winner determined on the basis of skill (i.e., through judging based on specific criteria).
   d. By “sweepstakes” we mean a promotion that includes a prize of monetary value and a winner selected on the basis of chance.

source from: https://www.facebook.com/promotions_guidelines.php