I know that it is against the rules of Facebook to harvest information from other users. What constitutes as harvesting information, though? If someone is your friend and you harvest their posts, for example, is that harvesting?
Facebook has very explicit rules in their terms of service and developer agreement about taking data. Of course how you use it greatly alters the issue… if you’re using photos in an app a user posts on your site and they know they are sharing them its much different than taking their photos off their profile and putting them on another website.