This is a great question and one that can be answered simply. According to the most recent facebook statistics, there are more than 800 million active users and more than fifty percent of them go on facebook everyday. And the average user has around 130 friends. In light of these facts, facebook is an incredible social media platform. It is increasingly popular and with the benefit of each user having a network of friends, it is a great way to communicate and advertise.
The relevance to potential companies should be obvious. If they are able to reach users through advertisement, then it will benefit them. Moreover, if they are able to get people to endorse their products or travel destinations, then it could be more powerful. And if a company wants a certain image, all they need to do is get the people whom they want to represent their companies to endorse their products. Facebook even has an easy way to do this; it is called "liking something." In short, it is an important platform.