Last week at SXSW Google engineer Matt Cutts announced that Google is working on an "over-optimisation" penalty. If your site is "overly seo'd" then expect to see your rankings start to fall in the coming months.
As far as I'm concerned, this isn't really news. It's an obvious progression for Google and it's something I've warned clients about for years now: you can't afford to focus on getting users onto your site at the expense of providing relevant content to them once they arrive.
Nevertheless, this latest step by Google is easy to understand. You just need to understand what business Google is really in.
Hint: It's not the search engine business.
Answer: When they're an overseas design sweatshop using dodgy SEO tactics.
I'm used to getting comment-spam on my blogs. Disqus is cleans out most of it automatically, but a few make it through to publication. Fortunately, Disqus sends out notifications on new comments, so I'm able to manually filter out anything that doesn't seem genuine.
Comment spam is used by dodgy SEO businesses trying to build backlinks for themselves or their clients. The idea is that you choose a blog that's relevant to the search terms you want to build PageRank for and insert a comment (genuine interaction seems to be unneccessary) that has a backlink to your site.
While this can build pagerank on the site you've linked to, it only works if the site you're spamming has a higher pagerank than your own and is relevant to the kind of keywords you hope people will use to find your own site.
It also won't help you if you get branded as a spammer by doing so.
Validating a website has become standard practice among designers over the last few years. As a site nears completion, the designer tests the site against the W3C Validator service to ensure that the code meets the standards, allowing them to proudly display a badge declaring their competency.
I have no real problem with this, except insofar as it provides no value (except to the designer's ego!) to show this badge.
The real problem lies with the claim that validation is inherently valuable as an SEO tactic. Sites like Google, Amazon and a plethora of other high-ranking sites stand as proof positive that validation alone will not ensure your site ranks highly.
So why is validation touted as an SEO technique?