if you read closely you will realize that they actually tell you that in advance under the terms and conditions.. Reciprocity and Replicating core functionalit

if you read closely you will realize that they actually tell you that in advance under the terms and conditions.. Reciprocity and Replicating core functionality: (a) Reciprocity: Facebook Platform enables developers to build personalized, social experiences via the Graph API and related APIs. If you use any Facebook APIs to build personalized or social experiences, you must also enable people to easily share their experiences back with people on Facebook. (b) Replicating core functionality: You may not use Facebook Platform to promote, or to export user data to, a product or service that replicates a core Facebook product or service without our permission. so developers can do themselves a great deal of good by developing on third-party platforms while respecting the terms and conditions specified for the said platform