Advice that was once solid morphs into myth as Google updates its secret sauce to drown out spam and improve the contextual relevance of its results. Last year, a significant update marked the shift away from using the link graph and keyword matching to a more semantic recipe based on the Knowledge Graph.
While the Knowledge Graph is complex and its explanation is beyond the scope of this article, semantic search can be boiled down to the return of relevant results, even when the page doesn't include the text queried.
This doesn't mean keywords aren't important - but they are less important in the sense you don't have to obsess over exact keyword matching as in the past.
What's changed since 2005?
Moz' famous Search Ranking Factors report, its biannual survey of experts and correlation study on nearly 15,000 search queries charts the course...
The top 5 ranking factors in 2005 were the title tag (keyword match within, and keywords close to the beginning as possible), anchor text of links pointing to your page, keyword use in document text, accessibility of the document, and links from internal pages.
In 2007, keywords in title tag still reigned supreme, with global link popularity of your site, anchor text of inbound links, link popularity within internal site link structure and age of site rounding out the top 5.
Contrast this with 2013's report:
Keywords in title tags, meta descriptions, headings and even body text matter less than links and social factors.
To illustrate, notice how a search for "Coach Naples" (a style of Coach brand shoes) returns results without the keyword term:
Searching for "coach naples shoes," results are much better. But again, exact keyword matches matter less.
These results are more likely influenced by a mix of strong link profiles, social likes and shares, the authority of the domain, whether a searcher has visited a site frequently in the past, click through rate history per keyword phrase, and sometimes local factors (are you in Naples, FL?).
So what are the takeaways?
1. Understand that keyword relevance is important, but less important than link building, social marketing and site performance tuning.
2. Perform keyword research and use a variety of semantically related keywords appropriately on your site, but don't be obsessive about it. Don't aim for a specific "keyword density" on your site, or place them in body headings unnaturally.
3. Avoid link-building specifically for keyword anchor text. Links are less valuable when they look like the product of link building efforts like guest posting (one signal is the unnatural use of a common keyword phrase in anchor text).
4. Focus most link building effort on links from topically related domains and pages. The semantic relevance of the linking domain and page also matter, so submitting a guest post on conversion optimization to a general marketing website, linking back to your motorcycle helmet store, for example, is not going to help the way it may have in the past.
5. Support social sharing from product pages through Like, Tweet and Pin buttons, and consider Google+.
6. Recognize that today's ranking factor may be tomorrows spam signal.
Also note, while semantic markup is not the same as semantic search matching, it can help you stand out in search results. If you are unfamiliar with this, please read our article on semantic markup for ecommerce pages.