Terms of service for Facebook apps
These rules and guidelines are put in place so that all of your app users know what they can or can’t do with the content you have provided to them. Terms of service will also usually contain measures which you can practice when someone abuses the app, the website, and its contents, and as such, this document is looked upon as a legal agreement.
Terms of service for Facebook apps is optional in the phase when you want to go from a development app stage to live app stage. In the live stage, you can test the app, but still can’t make it public to users.
Once you have decided to make it public though and allow Facebook users to use it, you will be asked by Facebook to include a URL to the terms of service.
By doing so, you are informing the users who log into your Facebook app, website or mobile app about the rules and guidelines they have to comply with.
This agreement is served in a click-wrap fashion, which has more legal power should some dispute go to court.