For years, many SEOs and webmasters maintained that Google would never penalize a site for incoming links. Only selling links could get your PR
stripped or your site penalized or removed from the index.
That's clearly no longer true. Buying links or being the recipient of bad incoming links” can now earn a Google penalty.
Google’s campaign against paid links ramped up in 2007, when the search giant sought to prevent webmasters from purchasing PageRank and the power of any other ranking signals, such as anchor text. The rel=nofollow attribute, which Google introduced in 2005 to help combat comment spam, was called into play. Webmasters should, Google said, indicate any paid links with the nofollow attribute. Webmasters were asked to report any paid links they knew about.
On Search Engine Land blog July 5, Barry Schwartz noted that Google started sending out more and more notices of penalization to sites selling links in January, 2011. This month, he said, there were reports
reports that Google is notifying webmasters that they have bad links pointing to their web site, as opposed to bad links on their web site pointing outwards.”
Part of a typical notification reads:
We’ve detected that some of your site’s pages may be using techniques that are outside Google’s Webmaster Guidelines.
Specifically, look for possibly artificial or unnatural links pointing to your site that could be intended to manipulate PageRank. Examples of unnatural linking could include buying links to pass PageRank or participating in link schemes.
We encourage you to make changes to your site so that it meets our quality guidelines. Once you’ve made these changes, please submit your site for reconsideration in Google’s search results.
If you find unnatural links to your site that you are unable to control or remove, please provide the details in your reconsideration request.
Purchasing links is an increasingly risky tactic.
Read the full report: Google’s Sending Webmaster Notifications About Bad Links Pointing At Their Sites