I'm a little late to this conversation. Everyone before me has posted a great reason for your business to start a blog.
From my experience, I started a blog for one company I was hired to turn around. In that blog, I talked about the challenges people were facing and gave them the answers they were seeking, so they would have confidence that we were listening to user concerns and that we were making progress. I would also post new development updates with tutorials on the blog, to give our users information about those new releases and how to implement them.
A blog is the voice of the company. Tying that blog to social - post notifications to all social media accounts when a new blog post is available, is a critical marketing tool.
I have found that there are two kinds of companies:
1. companies that want to say something
2. companies that fear saying something
The companies that want to say something are eliciting trust and generating the authoritative voice that customers today want to see. Be silent and learn that silence is deadly. Today, transparency wins you good will. Be vocal and learn that your exuberant enthusiasm will generate excitement for your brand and new fans, partners and friends.
That's my advice, for what it's worth. I never again want to work with a company that wants to hide information out fear that seeing some negative replies is a bad thing. Remember, you can always control/moderate comments anyway. If you don't give your target audience any information that can be found in a Google search, then you're pretty much acting like the second example I provided.