Here’s what Facebook has written:

“A Like that doesn’t come from someone truly interested in connecting with a Page benefits no one. Real identity, for both users and brands on Facebook, is important to not only Facebook’s mission of helping the world share, but also the need for people and customers to authentically connect to the Pages they care about. When a Page and fan connect on Facebook, we want to ensure that connection involves a real person interested in hearing from a specific Page and engaging with that brand’s content. As such, we have recently increased our automated efforts to remove Likes on Pages that may have been gained by means that violate our Facebook Terms.” Read the entire post- https://www.facebook.com/notes/facebook-security/improvements-to-our-site-integrity-systems/10151005934870766