Some data-processing is an intrinsic part of running a social networking site. That's not being complained about. What is being complained about is the secret data collection and processing that's happening without the user's permission or knowledge - visiting a page with a like button gives data about the user to Fb even if the user doesn't click the button. Fb then use that information to do stuff.

Since the user has no way of knowing if a page he's about to visit will have a Fb like button or not; and the user probably doesn't realise that Fb will gather the data with no user interaction on the button; that seems like excessive collection and processing.