The big mistake some startups make with company blogs
blog.invantory.com
blog.invantory.com
* Not linking prominently to their main site. (rdl is right on the money.)
* Using Google AdSense or similar programs on their blog. Sending away prospective customers for pennies is far from a good plan.
* No calls to action. Insightful articles are nice, but you need to lead the reader to take action, whether it's signing up for your newsletter, RSS feed, checking out your main site, a particular product, simply get in touch to say hi, or something else.
* Targeting the wrong audience. If you are blogging for customer acquisition, you need to answer the questions your customer base has. Blog about the information they are after. BTW, your audience is not everybody. Your audience is a specific, narrow group of people.
* Failing to promote their posts. Build it and they will come doesn't work in the blogging world.
In terms of your point about calls to action, I feel that insightful posts aren't just "nice," if they are truly informative or useful to the reader the CTA should be obvious -- this is the kind of company I want to find out more about, or I am going to follow the company/author on twitter. But that also ties into your first point -- make sure readers can take that action on their own by linking to the main site/Twitter feed/etc.
Absolutely. You could for example have posts aimed at recruiting talent. The key is targeted blogging, instead of posting randomly (which many startups do).