Search engine optimization (SEO) is not an exact science, and many of the so called gurus tend to make it sound a lot more complicated than it really is. A combination of on-page and off-page factors are responsible for the ranking of a website in the search engines. Google is the largest on the search engine companies and really does have the lions share of the market, claiming around 90% of the search traffic, with Yahoo and Bing as the second and third place companies, but only getting a small percentage of the searches.
There is little doubt that during 2011 the landscape has changed for search, and websites and article directories have been hot very hard by updates, in particular the Panda updates that Google have rolled out in the last few months. The issue seems to be one of thin content, content and sites that are only online purely for the monetization potential, and not offering a user experience that Google has chose to define. While this quality user experience may be tricky for us mere mortals to define, the SEO strategies do not need to change dramatically, but as SEO professionals, we need to implement additional measures to allow ourselves to remain competitive.
Good content, with keywords in title, description, title tags, and liberally sprinkled throughout the content are still relevant. Alt text for images is still a good idea. The use of latent semantic indexing (LSI) to them your content is still a good strategy. Internal link structures and good site navigation are essential to offering a good user experience.
Off page strategies like link building are important. Sure, we have all ranked pages with no links, but the inbound links certainly help to increase the perception of value of the page in the eyes of the search engines and their dastardly spiders.
One thing that may well have played a part in Panda updates, as well as thin sites and duplicate content, is link quality. SO many people have been building links with mass article submission software for a long time, and it is likely that the links that came from those hundreds of low quality article directories have been devalued. This is perhaps one factor, but there are certainly many others that we will never hear about.
Social factors like adding Twitter and Facebook buttons to your page will certainly play a larger role in the future. We need to adapt, but not to discard what we already know.