Facebook has recently improved anti-spam controls as noted below

http://facecrooks.com/Internet-Safety-Privacy/Facebook-Tells-Page-Owners-Stop-Spamming-News-Feeds.html/

http://newsroom.fb.com/news/2014/11/news-feed-fyi-reducing-overly-promotional-page-posts-in-news-feed/

QUOTE: Facebook announced this week that it has once again tweaked its News Feed algorithm based on a user survey, and will now devalue “overly promotional page posts.”

According to Facebook, they want to get rid of spammy page posts that push people to buy a product or download an app, encourage them to enter contests or sweepstakes and posts that simply reuse content from Facebook ads. Though concerns have already been raised that this change is simply a way for Facebook to boost its own revenue by moving advertising from promotional posts to Facebook ads, Facebook vehemently denied the new algorithm will lead to any more ads.

“This change will not increase the number of ads people see in their News Feeds,” the site wrote in its announcement. “The idea is to increase the relevance and quality of the overall stories – including Page posts – people see in their News Feeds. This change is about giving people the best Facebook experience possible and being responsive to what they have told us.”