It depends what you are trying to achieve with a blog a bit to, are you trying to address customers, prospective customers primarily or are you trying to become

It depends what you are trying to achieve with a blog a bit to, are you trying to address customers, prospective customers primarily or are you trying to become an authority in your niche by writing about it more broadly and picking up a lot of search traffic. I think a great example for authority is SEOMoz, provides value well beyond the actual product.