Why hire a professional?
The world is full of boring stuff, which is why so few people pay attention. Great design and marketing is the art of building things worth noticing right into your product or service. Not just slapping on the marketing function as a last-minute add-on, but also understanding from the outset that if your offering itself isn't remarkable, then it's invisible -- no matter how much you spend on well-crafted advertising.
This is an not to convince you why we are right, but what it tales to make work that is right—to create and sell something remarkable. It is for companies who want to make a difference in their company by helping create products and services that are worth creating / marketing in the first place. It is a plea for originality, for passion, guts, and daring. Not just because going through life with passion and guts beats the alternative (which it does), but also because it's the only way to be successful. Today, the one sure way to fail is to be boring. Your one chance for success is to be remarkable.
So why would you trust your nephew with your brand even if it was just for a website build, or ask an intern to learn HTML, or generally trust your success to anyone other than the very best?
Communicating your brand can be a very complex thing, requiring an ever-increasing level of expertise to build. That's why you should interview qualified teams to lead these initiatives. The best way to evaluate their work is to see examples of their sites and speak to their previous clients. Search for someone who best suits your needs and personality. The time it takes to find the right fit will pay off in the long run.