Become the site you want a link from
That's a pretty great way to put it.
I use it for one thing - long tail searches
And if you watch the analytics and see you get a dribble of traffic from a term you don't expect, that's a sign you can rank for that term and can put more effort into it.
That said, I was thinking more broadly still. Let me ask yet another question: If you came up with a strategy that got you banned from Google entirely, but year after year would bring in five times as many visitors and with better targeting and conversion rate than your visitors from Google, would you do it?
This is what I meant by my comments on blogs, Facebook pages and newsletters. I can think of one product right now that I have never purchased, but their blog is so good that I have both an email and an RSS subscription. If Google bans them tomorrow, they will be able to reach me forever with good content that gets me to click through to their site and, hey, they're running a special.
I recently took an actual go in to work job (really the first in my adult life). The social media presence was sort of perfunctory. Regular posting, but without any real jazz to it.
My colleague is primarily responsible for social media, though I've done a little, but in the first month we've dramatically increased Facebook reach. He's had some posts that just kill it, but even though I don't really do social media, I did one short post that had a reach of 8,000 and got almost 200 shares and comments. More importantly, you can see "likes on shares" which are mostly people who don't follow us who are liking the post on their friend's feed. And some of the comments were passionate and beautiful from ultra-engaged customers. If nothing else it made me proud that people feel that way about us.
So does that Facebook page help with SEO? Well, it's never going to show up in Webmaster Tools or Open Site Explorer or Majestic or whatever.
1. "likes on shares". That's killer in and of itself
2. long-term spillover into blogs, review sites, etc.
3. thousands of people per week we're now reaching without entering the Googlesphere at all.
So my original point was basically just a riff of Martinibuster's original point in the thread I referenced: don't get so low in the weeds that you can only see this or that exploit of the Google algorithm. There was a time when you could hit a home run with that sort of thinking. In the Penguin/Panda/etc world, that is only going to get you the smallest incremental gains.
Think of overall goals, broad strategy and making yourself engaging and useful. Then don't do stupid things in terms of SEO.
If you have the best technical SEO achievable and you are completely uninteresting and unengaging, you're screwed.
If you have content and products and insights and services that people love and care about, if every aspect of your business shows that you put customers first and care about them and want them to become repeat customers, you can get a lot wrong on SEO and Google will still be your friend.
Which brings it all back to Martinibuster's quip
Become the site you want a link from
Except I'm going to broaden that and say
Become the business you would want to engage with
How you start is up to you, whether that's a blog, a Facebook page, a newsletter, a conference you sponsor (did Brett build Pubcon to what it is now because it was good for SEO for Webmasterworld? I could probably ask my original question a hundred different ways) or whatever.
But if you want an answer to your original question...
If you have the time, energy and other resources to put into a blog (be honest with yourself*) that will say something new that other people aren't saying and that your customers would find useful and interesting, that your target audience would add to their RSS reader and share on Twitter, there is no question you should have a blog.
If you are starting a blog because it's "good for SEO," then please don't. The internet doesn't need your content.
And BTW, I've tried to write regularly for a small business where the business owners were disengaged from the blog. I did my best, but it was a business in a tough niche that I knew nothing about and cared about even less. That blog got no traction. I was learning the landscape, though, and think if I had kept going for two years, it would have worked, but they were not willing to pay for a blog post a week for two years to find out and they were not willing to personally write even a blog post a year. But since they wouldn't even take the time to log into Facebook and like their customers back and wouldn't log in to LinkedIn (more important to them than FB as it was B2B) and accept link requests from customers, it was impossible. They wanted SEO to be a magical divination of the Google algo that would give them results in 6 months.