Every two years, SEOmoz surveys top search engine optimization experts all around the world on their opinions on search engine ranking factors that affect search engine optimization.
In 2009, they did the same thing again (they are doing for 2011). I think this document is one of the most useful resources for SEO practitioners and especially important for Malaysian SEO consultants since we don't have many surveys done in Malaysia for the same topic.
As you can see, 4 out of 5 factors are link buildings. If content is king, then link building is queen. Keep producing great content for your websites or blogs is not enough if you don't have quality links to show Google your websites have high authority.
While for top 5 negative factors, the highest is cloaking with malicious/manipulative intent, followed by link acquisition from know link brokers/sellers (so don't buy links), links from the page to web spam sites/pages, cloaking by user agent and frequent server downtimes & site inaccessibility. The one I experienced the most is the last factor – frequent server downtime & site inaccessibility, which was 5 years ago.
I am very excited about the 2011 surveys. Hopefully it can be done as soon as possible.