When to Create an Author Page?

The answer to this question has eluded me for the past few weeks. At what point does an author create a "fan" page?

As we all know, social media is one of the most popular things on the internet right now. Facebook, Google+, Twitter, and so on. There are so many ways for people to advertise, it can sometimes be hard not to get overwhelmed. Facebook is one of the most popular, if not the most popular form of social media out there, and everyone has the option to create their own "page." I'm...