The way I understand it, it is best to join WA if one has a business to promote. The business should ideally be one that he is passionate about or in line with his own interest. He can then use the knowledge and technology learned from WA to build a website concerning his product or service, drive traffic to the website and hopefully, generate sales from his visitors.
Larger enterprises can hire an agency or full-time staff member to run their social media accounts, but small businesses often have to handle their own social media marketing. With so many responsibilities, business owners are often too busy, overwhelmed or undereducated about the importance of a social media presence to spend time developing and implementing a great social media strategy. As a social media consultant, you can help small businesses determine the best tactics, posting schedules and content for their target audience. As their follower count grows, so will your business.