Those users who are not aware of the fact that they can only get Facebook Credits if they buy them, earn them or receive them from friends, can be easy targets for this rather legitimate looking scam:
The page in question - located at freefb-5000.blogspot.com and still available - continues to convince the user of the legitimacy of the offer: "You might be thinking how this works. Well, this works because of the advertisers and sponsors who pay us for every promotion. So don't thank us for the free credits, thank our great sponsors!"
To get the free FB Credits, the user is required to jump through a few hoops. He must share the page, post about it and then "Like" four other pages.
In the end, the user is taken to a page where he is asked to complete a survey. Do I need to point that there are no free FB Credits waiting for him once he has performed all this?