Do you know the names of the reporters who cover your industry? If you are a flack you do; but if you are a business owner you might not. You might know who your favorite reporters are, but not everyone who covers your industry. You should know them (or hire someone who does know them). If those reporters are on Twitter, you need to follow them.
You should follow your customers, your competitors, your employees (not to check up on them, but to learn from them, have some faith in your hiring process), industry analysts, and anyone prominent in your industry.
Social media is your virtual store front window. It gives prospects and reporters a chance to view your business in a very low pressure manner. It gives them a preview of what to expect.
Social media is the online version of the social hour before a business meeting. It is an occasion to exchange gossip and get to know people personally. In other words, social media is a chance to strengthen existing relationships and build new ones. That is why too much attention to SEO and search engines is so destructive. It diverts your attention from where it needs to be, on your human audience.