The concept of "comment marketing" is not that new: leave comments that get eyes back on you. But the tactics have changed.
The "web log", or "blog", as they've become lovingly know, has become the hallmark of the small-scale written world made possible by the fact of the internet.
And the blog is now becoming a very powerful force in the building of high-quality traffic and links that point back at you.
The "Black Hat" spam comment techniques are as dead as Lady Gaga's meat dress: hiring robots to simply crawl the web and post spam pointing links back to you died as a relevant way to get a higher Google rating about 4 algorithm updates ago.
But if you can begin to build authentic community, then all these things shall be added unto you, full measure pressed down and overflowing.
The rule is simple. People write because they want to share what they know and how they feel. And people love validation. So find some people who are "influencers" (not necessarily "customers" or "prospective customers" and read what they have to say. Then comment. Not just "Great stuff, man," but something witty and poignant, meaningful and impactful.
Find 3 to 5 blogs that are influential in an area related to what you do, and comment. Often. Agree. Disagree. Challenge. Praise. Always be respectful, but don't hesitate to tactfully engage the author.
The SEOMoz guys go further in the the video above, trying to make sure your self-brand is as consistent as possible across all formats. Use the same image, always (and possibly professionally done).
Of course, you should have a blog where you can share your findings, thoughts, etc too.
And of course, you should comment below 😉