Search Engine Optimisation (SEO) is a growing yet unstable industry. It's not the proverbial castle built on sand but it's certainly a castle built on a fault line.
Just last week, Google's Matt Cutts caused a ripple tidal wave in the SEO community by putting the kybosh on PageRank Sculpting.
PageRank Sculpting is was one of those SEO techniques that befuddled customers and earned the black hat tag. The kind of thing SEOers love - nobody understands it and we can charge lots for it!
So which SEO techniques do work? Well, Silkmoth have repeatedly said that there's no better way of driving visitors to your site than adding more content. You can't have enough content. If visitors find the content valuable then so will search engines. Traffic will follow.
In a response to a comment on his blog Matt Cutts puts it as well as anybody...
Search engines want to return great content. If you make such a fantastic site that all the web has heard of you, search engines should normally reflect that fact and return your site. A lot of bad SEO happens because people say “I’ll force my way to the top of Google first, and then everyone will find out about my site.” Putting rankings before the creation of a great site is in many ways putting the cart before the horse. Often the search rankings follow from the fact that you’re getting to be well-known on the web completely outside the sphere of search. Think about sites like Twitter and Facebook--they succeed by chasing a vision of what users would want. In chasing after that ideal of user happiness and satisfaction, they became the sort of high-quality sites that search engines want to return, because we also want to return what searches will find useful and love. By chasing a great user experience above search rankings, many sites turn out to be what search engines would want to return anyway.
The elves are back...