Gaining Google's trust doesn't happen overnight. It takes time. Think about building up your relationship with anyone. The longer you know that person, the more likely that trust will solidify. So, the reasoning is, that if Google just met you, it's going to have a hard time trusting you. If you want Google to trust you, you have to get other people that Google already trusts, to vouch for you. This is also known as link-building.
In a number of recent articles, where I've interviewed some of social media's rising stars such as Jason Stone from Millionaire Mentor, Sean Perelstein, who built StingHD into a global brand and Nathan Chan from Foundr Magazine, amongst several others, it's quite clear that multi-million-dollar businesses can be built on the backs of wildly-popular social media channels and platforms.
Digital marketing is defined by the use of numerous digital tactics and channels to connect with customers where they spend much of their time: online. From the website itself to a business's online branding assets -- digital advertising, email marketing, online brochures, and beyond -- there's a spectrum of tactics that fall under the umbrella of "digital marketing."