Facebook has been hiding status updates for years. Facebook accomplishes this by adjusting your newsfeed according to which people, topics and events you care about. If you Like a series of DJs, Facebook will ensure DJ-related posts get seen. If you Hide Updates from all of your overly-political friends, Facebook will reduce the visibility of politics in your feed. Again, Facebook has been trying to increase user retention using data mining for years. Adjusting your newsfeed to what you find relevant is about making a better experience to the user.
Casey Johnston's article in ArsTechnica elaborates:
...if your news feed was an equal-opportunity space, it would be at this point nothing but offers for FarmVille produce and a thousand status updates on everyone's new babies. Should that happen, your interest in checking the service might wane. Facebook doesn't show you everything every person or brand you subscribe to says, and it's always been that way.The only difference with Promoted Posts is that now you can increase your posts' "newsfeed importance" for really important posts, such as announcing a new album.
The article continues:
Facebook told Ars separately that the converse of this statement is also true: if a post receives few or mostly negative reactions, it is more expensive for the page owner to promote than if the post were popular on its own, and such posts don't reach as far. The goal is to make sure that even promoted posts feel relevant and interesting to read.Making it harder for crappy posts to fill up your newsfeed is a very, very good thing.
Promoted posts provide a balance between keeping advertisers (paying customers) happy while not scaring away facebook users (data for paying customers) with cluttered newsfeeds. Considering Facebook's terrible stock performance it's a surprise the measures the company has taken to make more money aren't more obtrusive.
So what's the final verdict on promoted posts?
If you're enriching your fans, you pay less and get noticed more. If you're wasting fans' time, you pay more and get noticed less.