Matt Cutts of Google has written two posts this weekend on links to start a mountain of discussion in the SEO community. How to report paid links and hidden links from Matt Cutts discussed how Google is in the process of testing out new methods to detect and handle paid links and their impact on the Google search results.
Specifically, Matt explains that Google is "trying some ideas" and "testing out some new techniques" to handle paid links. Exactly what this means, I am not sure. Does it mean Google will just not count those paid links? Does it mean Google will trust the links on a site with paid links less? Does it mean that Google will devalue a site that sells paid links? Does it mean Google will devalue some of the sites selling paid links, based on how they document the links as paid? Again, I am not sure.
It is clear from Matt's hidden links post that if you do have paid links on your site, you should preferably label the links as paid for both human visitors and the search engines.
To make sure that you’re in good shape, go with both human-readable disclosure and machine-readable disclosure, using any of the methods I mentioned above.
So for search engines, you can use the nofollow attribute or a redirect script. And for humans, just label the link as a paid ad, paid review, sponsored section, or something similar.
In addition, Matt is asking for those who know of paid links, to report them via Google Webmaster Central or Google's spam reporting form.
Source:→ SELGoogle, Matt Cutts, Links, Link building, Paid Links