Should professional websites have blogs?

My primary business is my digital risk consulting business and its website has a blog along with static pages about me, my services as related themes. I have maintained a blog on my professional sites for about 9 years, it just seemed like the right way to set up a professional site. Lately, though, I’ve been wondering whether I should separate my blog from the static site?

Sam Glover wrote a post titled “Get Your Law Blog Off Your Law Firm Website” on Lawyerist a while ago and I pulled it out of my Instapaper archives to read again. Glover makes an argument for why professionals, particularly lawyers, should maintain a separate blog because it’s function is different.

Blogging is long-game marketing. When you have a well-read blog, you earn your own media every time you post something. You don’t need to wait around for the local news to call you for your analysis of the latest celebrity divorce or corporate bankruptcy (although if you have a good blog, they probably will); you can just publish it yourself.

But in order to build that audience, your blog is better off on its own website, with its own look and feel. Your blog should appear to be (and actually be) a publication, not a law firm’s marketing website.

The basic idea is that people visit law firm websites when they are looking for a lawyer and only stay on the site long enough to assess whether the firm can help them out. On the other hand, people who find a professional blog they find informative keep returning for more content, not necessarily because they Google’d something they need help with.

That makes some sense to me although I have maintained a blog on my business sites because my thinking was that having a blog there keeps the site dynamic (assuming I publish regularly) and that keeps Google and other search engines interested. Perhaps my thinking is dated and/or no longer valid?

Is a blog on a professional website an attempt to mix oil and water, metaphorically speaking? Does that model hinder both from being more effective on their own?

If it is better to separate the two, I’m tempted to merge the WTL blog into this one. On the one hand, doing this enables me to write more fluidly and focus my writing on one blog and, on the other hand, keeping a focused blog maintains the niche I created and better serves readers who are only interested in that content.

I’m sure this stuff used to be simpler back in the day when blogging was still new. Any thoughts?