The title is a bit of a link bait, the video which was posted in an earlier thread (https://news.ycombinator.com/item?id=7211514 https://news.ycombinator.com/it

The title is a bit of a link bait, the video which was posted in an earlier thread (https://news.ycombinator.com/item?id=7211514 https://news.ycombinator.com/item?id=7211514) stated that, through Facebooks paid ads you also get likes from click farms (presumably because click farms like pages they aren't paid to like in order to avoid detection). This means that a higher percentage of your likes are from click farms than if you gained your likes organically, so when you pay for a post to reach a set number of your fans, a larger percentage of that is lost to click farm users who you don't want, than if you had purely organic likes.