Google has laid down the defining lines in the battle of link building and the value of link popularity. In summary, the old motto, an earned link is the best link, still outranks almost any form of link building imaginable.

Essentially, if a link is earned due to quality, ideas, originality, or via establishing a site, persona, or business as a resource; chances are, that link is going to be of high value in the Google ranking algorithm:

Discounting non-earned links by search engines opened a new and wide field of tactics to build link-based popularity:

- Classically this involves optimizing your content so that thematically-related or trusted websites link to you by choice.

- A more recent method is link baiting, which typically takes advantage of Web 2.0 social content websites.

- One example of this new way of generating links is to submit a handcrafted article to a service such as http://digg.com.

- Another example is to earn a reputation in a certain field by building an authority through services such as http://answers.yahoo.com.

Google's advice is: Always focus on the users and not on search engines when developing your optimization strategy. Ask yourself what creates value for your users. Investing in the quality of your content and thereby earning natural backlinks benefits both the users and drives more qualified traffic to your site.

Get the full story at the Offical Google Webmaster Central Blog