If Google engineer Matt Cutts had his druthers, buying links would become an extinct SEO practice.
Cutts has addressed the topic of link-buying on a number of occasions on his blog and in blog comments elsewhere. He's admonished webmasters who buy links for PageRank and encouraged webmasters instead to buy only links that have been "nofollowed" — in other words, where the rel=nofollow attribute has been added to the link so that the search engines do not count that link as a vote. He has stated in no uncertain terms that Google considers "buying text links for PageRank purposes to be outside our quality guidelines."
Cutts outed the Berkeley college newspaper on his blog as a link seller. Cutts then warned that sites such as Dailycal.org that sell links may "lose their ability to give reputation."
In other words, Google may revoke the site's voting power — its ability to pass PageRank. That is of course disastrous for the link seller, but it is also bad news for the link buyer, who is unwittingly wasting money every month for that link.
In a comment on the O'Reilly Radar blog, Cutts revealed that "parts of Perl.com, Xml.com, etc., have not been trusted in terms of linkage for months and months." His comments were significant: Google admitted it decreased the voting power of such excellent and useful sites as Perl.com and XML.com and downgraded the reputation value of some of the sites' outbound links.
Beware of links?
The implication for the rest of us is clear: if you don't want your site to suffer the same fate, you'd better tag your link ads as rel=nofollow so your advertisers won't gain any PageRank.
How do you detect if a site has lost its ability to pass PageRank? Unfortunately, it's not easy.
Cutts cautioned: "Remember that just because a site shows up for a link: command on Google, [that] does not mean it passes PageRank, reputation or anchortext." There is, in fact, no way to know for sure — unless you work for Google on its Webspam team.
A link buyer can surmise the loss of the link seller's voting power by a drop in his/her rankings commensurate with a drop in the rest of the link buyers' rankings. Consider the case of link-selling California newspaper The Fresno Bee. At some point in time between 2004 and 2005, its reputation was rescinded by Google, as indicated by the hurried exit of nearly all the link-buying advertisers (which you can verify through the Internet Archive's Wayback Machine).
When diagnosing whether a link seller still has his/her voting power, one tool I find helpful is the SEO-Links extension for Firefox. Simply hovering over the paid links allows me to quickly obtain rankings for the keywords targeted in the anchor text. The inference is that a site stacked with successful link advertisers is probably contributing to the rankings. If it weren't, all those SEO-savvy advertisers probably wouldn't be there.
What do SEO pros think?
Not surprisingly, search engine optimizers have a different view from Google on the issue of link-buying.
Christine Churchill, president of SEO consultancy KeyRelevance, describes the situation thus: "Search engines like to take the hard line and categorize things as either black or white. In some cases, they are actually grey. Taken to the extreme, your link from the local Chamber of Commerce could be considered link-buying."
Indeed, a $300 annual directory submission to Yahoo! is, in effect, a paid link. But Google allows that one since there's an editorial review process involved.
Personally, I think link-buying can be done legitimately, just like in the case of a Yahoo! directory submission. I don't see the difference between a banner ad and a text-link ad — as long as you're not intentionally trying to game the search engines and you expect to get traffic and brand visibility from the ads you place on websites.
To me, it seems unreasonable for Google to expect website owners to ensure that no PageRank is transferred in all the online advertising it facilitates. It is however, up to you, the advertiser, to ensure that all ads are placed on relevant websites and are not misleading, whether text-link ad or banner ad. It is then the publisher's responsibility to screen all advertisers for relevance and ethical SEO behavior.
A site with paid links that span the spectrum of relevance — from casinos to mortgage brokers to pharmacies to jewelers to electronics merchants and all places in between — is certainly an obvious red flag to the search engines. Reputation should be passed only when the publisher can confidently vouch for the link ads and the sites to which they point (and to the sites to which they, in turn, point).
This is where a reputable and highly selective text-link broker, such as LinkExperts, can be invaluable, as you vet both the publishers and the advertisers.