Wikipedia has announced that all of its outgoing hyperlinks will now include the rel=”nofollow” attribute, which instructs search engines to disregard the links. Search engines infer a page’s importance by seeing who links to it – pages that get many links, especially from important sites, are deemed important and are ranked highly in search results. A link is an implied endorsement: “link love”. Adding nofollow withholds Wikipedia’s link love – and Wikipedia, being a popular site, has lots of link love to give.
Nofollow is intended as an anti-spam measure. Anybody can edit a Wikipedia page, so spammers can and do insert links to their unwanted sites, thereby leeching off the popularity of Wikipedia. Nofollow will reduce spammers’ incentives by depriving them of any link love. Or that’s the theory, at least. Bloggers tried using nofollow to attack comment spam, but it didn’t reduce spam: the spammers were still eager to put their spammy text in front of readers.
Is nofollow a good idea for Wikipedia? It depends on your general attitude toward Wikipedia. The effect of nofollow is to reduce Wikipedia’s influence on search engine rankings (to zero). If you think Wikipedia is mostly good, then you want it to have influence and you’ll dislike its use of nofollow. If you think Wikipedia is unreliable and random, then you’ll be happy to see its influence reduced.
As with regular love, it’s selfish to withhold link love. Sometimes Wikipedia links to a site that competes with it for attention. Without Wikipedia’s link love, the other site will rank lower, and it could lose traffic to Wikipedia. Whether intended or not, this is one effect of Wikipedia’s action.
There are things Wikipedia could do to restore some of its legitimate link love without helping spammers. It could add nofollow only to links that are suspect – links that are new, or were added by an user without a solid track record on the site, or that have survived several rewrites of a page, or some combination of such factors. Even a simple policy of using nofollow for the first two weeks might work well enough. Wikipedia has the data to make these kinds of distinctions, and it’s not too much to ask for a site of its importance to do the necessary programming.
But the one element missing so far in this discussion is the autonomy of the search engines. Wikipedia is asking search engines not to assign link love, but the search engines don’t have to obey. Wikipedia is big enough, and quirky enough, that the search engines’ ranking algorithms probably have Wikipedia-specific tweaks already. The search engines have surely studied whether Wikipedia’s link love is reliable enough – and if it’s not, they are surely compensating, perhaps by ignoring (or reducing the weight of) Wikipedia links, or perhaps by a rule such as ignoring links for the first few weeks.
Whether or not Wikipedia uses nofollow, the search engines are free to do whatever they think will optimize their page ranking accuracy. Wikipedia can lead, but the search engines won’t necessarily nofollow.