A very convincing video from Veritasium video blog suggesting that advertising on Facebook actually damages your presence online.
The thing that is most concerning is that Facebook does not appear to be in control - the "Fake Likes" are a mask for link farms and thus even legitimate advertising gets targeted by the farms in order to disguise their activities.
This is a massive problem for FB. We do not have a presence but I cannot imagine why advertisers would not pull their campaigns until this issue is properly addressed. To spend money damaging your brand is just crazy.
I know first-hand that Facebook's advertising model is deeply flawed. When I paid to promote my page I gained 80,000 followers in developing countries who didn't care about Veritasium (but I wasn't aware of this at the time). They drove my reach and engagement numbers down, basically rendering the page useless. I am not the only one who has experienced this.