Google claimed in a recent post that "Please be wary if someone approaches you and wants to pay you for links or "advertorial" pages on your site that pass PageRank. Selling links (or entire advertorial pages with embedded links) that pass PageRank violates our quality guidelines, and Google does take action on such violations."
What can be happening as a result of penalty?
Linkselling site start with losing trust in Google's search results, and then may get:
- lower PageRank in the Google Toolbar
- lower rankings
- in an extreme case, removal from Google's search results
Google said, If you receive a warning for selling links that pass PageRank in Google's Webmaster Tools, you'll see a notification message to look for "possibly artificial or unnatural links on your site pointing to other sites that could be intended to manipulate PageRank." That's an indication that your site has lost trust in Google's index.
How to fix the problem, if you want
To address the issue, make sure that any paid links on your site don't pass PageRank. You can remove any paid links or advertorial pages, or make sure that any paid hyperlinks have the rel="nofollow" attribute.
After ensuring that no paid links on your site pass PageRank, you can submit a reconsideration request and if you had a manual webspam action on your site, someone at Google will review the request. After the request has been reviewed, you'll get a notification back about whether the reconsideration request was granted or not.
Google is serious about link selling. Hope you take it seriously.