Vaspers the Grate has a terrific post on why You are Not a Blog:
You are not a worthy topic for a blog. You are interesting only to yourself, and even to that audience, only interesting intermittently.
This is true for both personal and business blogs. Especially business blogs. Customers will not come back to your blog to hear a bunch of self-important pronouncements about your products, services or company. Talk about something interesting to them. And then listen. Make it a conversation.