I have brought this up before that the goals and objectives of the various stakeholders in Advertising/Marketing do not work in Synergy. In fact it is a very dysfunctional ecosystem.
To highlight this recently Ad Age had an article about Facebook replacing Google as the disruptor of online advertising and when you read the article it becomes clear. If your business makes money by this being true you agree with the power of Facebook for marketing. This means Facebook, App makers, and Social Media Agencies care only about spending as much of your money as they can get from clients and thus Facebook is a must spend. If you are on the Brand or Strategy side you care about selling the most product at the least amount of spend and want to look at all options and maybe Facebook is not the best place to spend money.
See what is wrong here? I can show Pepsi how to spend 10% less on Paid Advertising and still achieve the same amount of sales. Pepsi's lead Agency has no incentive to reduce their billings 10% and do the same thing.
When I talk to clients I advise them that even if they do not hire me, that they need an objective voice who is on their side. Every platform/media channel that offers paid advertising will tell you they are the best fit for your Brand. Every Agency will steer you to what they do for a living ie: TV, Print, Digital etc. They will all have a spin and none of them will give you a pay for performance offer. In fact they will all offer you more ways to sink money into the same hole.
There is nothing wrong with businesses and people being motivated by money and their own self interest. But hiring a consultant to work on strategy or help you decide if your money is being spent well is a great idea.