SEO Junkie

On his blog SEOBook, Aaron Wall points out that an abundance of low quality links could cause decreased importance in crawl priority as told by Matt Cutts over at ThreadWatch.

Matt also made a detailed post on his blog saying that some sites are completely removed from Google’s index due to heavy reciprocal linkage.

The sites that fit “no pages in Bigdaddy” criteria were sites where our algorithms had very low trust in the inlinks or the outlinks of that site. Examples that might cause that include excessive reciprocal links, linking to spammy neighborhoods on the web, or link buying/selling. The Bigdaddy update is independent of our supplemental results, so when Bigdaddy didn’t select pages from a site, that would expose more supplemental results for a site.

Aaron further explained the issue:

Knowing that having a certain percentage of shady links will kill your ability to rank in Google adds an additional opportunity cost to building shoddy links which. Things that were once “cheap” or “free” suddenly became expensive, and quality votes gained a bunch more value in the process as well.

Thus, it is extremely important that you be extremely cautious while building links to your site. Don’t engage in excessive reciprocal linking and avoid linking to spammy neighborhoods on the web.