Link building is a critical component when it comes to building keyword visibility for search results in search engines like Google and Yahoo.
All search engines incorporate the quality of links, and the volume of quality links associated with a Website when assessing the site’s “overall value” online. In addition, links to and from websites and within websites are the critical mechanism that allows search engine programs (spiders) to get all of the different pages on the Web.
While search has and will always improve in its ability to index content without the necessity of links (a la Google sitemaps, My Yahoo and My MSN, Delicious etc), inbound link relationships will always be a factor.