Big or small, your business needs an independent Advisor for Marketing. Even if you have a Marketing Department it would be wise to have a second voice. A CMO is supposed to do this for you. Make sure you incentivize them properly so that a potential vendor you might spend $50mil with can't buy their way in. Trust me if you don't align compensation and make sure plenty is there, people can be 'bought'. Take it from an Ex-Salesperson who has spent plenty of Lunches and Dinners and Sporting Events on my employers dime entertaining clients or potential clients. Good news is most people can't be bought, they want to stay in their job and they have loyalty and decent ethics. But you would be surprised.
There are also plenty of trustworthy souls who don't have their own agenda besides your success such as your friendly Aliens at Sky Pulse Media . Sorry it's our blog we can plug ourselves. There are all manner of small agencies with no bias or platforms to sell you. Most have connections with people who have answers they are not an expert in. Most will come at a reasonable price.
Think of these types as your personal Lawyer who looks after your marketing budget. There are all sorts of reward systems you can work out to ensure when you succeed they benefit too. But the real driver for this post is Bias. Monetary Bias drives most businesses. Ask any business what is the best choice for your company whether it be a product or service and most will recommend something they make or service they offer. Even if there are options that are a better fit.
Think about it. If you go to a TV Agency the answer is More TV! A Media Buyer? More Media! I want to do Mobile Marketing Google will tell you Ad Mob. JagTag will tell you 2-D Barcode is best choice. Viacom wants to sell you Billboard space and Cable TV Commercial time. How do you know who to believe? They are incentivized to sell you their platform or service. They invested heavily to build now they need a return on that investment.