"Facebook says it uses pattern recognition to find and eliminate click farms and accounts that exist solely to like pages. Since March, says Facebook, it’s “notified 200,000 Pages that we’ve protected their accounts from fake likes.” I love the way they put this: “Protected,” as if the companies hadn’t paid for them."

This may be more accurate than the author of this article believes. I've read elsewhere that precisely because FB is using pattern recognition to combat this, the cleverest of the fake accounts spend a certain amount of their time doing random/normal stuff to avoid detection. And this includes liking random businesses. And one of the problems is that if a legitimate business pays FB to promote one of their posts (so it is shown to a bigger percentage of their followers), then the more fake followers they have, the more real money they are wasting to advertise to bots. So if a business is actually using FB to engage with their userbase, then the fake likes are in fact detrimental to them.