Bloggers: stop linking to Wikipedia
Based on a "directive" from Jimmy Wales , the English version of Wikipedia has started using the "nofollow" tag on all external links (the foreign language versions had been doing that for a while). That tag tells search engines to not pass any "search engine juice" (e.g., PageRank) from the WP page to the linked page. While sites that have links in WP will continue to receive visitors from those links, they will (supposedly) not receive search engine-related benefits (they might, however, be spidered by some engines). Certainly, some search engines may special-case WP (including having assumed that external links weren't trustworthy already), and some mirror sites (like answers.com) may or may not follow WP's lead. However, it's the thought that counts, and this is an example of WP giving a big FU to those who contribute to their site.
The rip-off nature of this change is described here:
What happens as a consequence, in my opinion, is that Wikipedia gets valuable backlinks from all over the web, in huge quantity, and of huge importance – normal links, not "nofollow" links; this is what makes Wikipedia rank so well – but as of now, they're not giving any of this back... Wikipedia has become a website that takes from the communities but doesn't give back, skewing web etiquette as well as tools that work on this etiquette (like search engines, which analyze the web's link structure).
That page also describes what I suggest that everyone does in response:
I predict some people will now, in return, stop linking to Wikipedia, or "nofollow" their links to Wikipedia (following the argument that if they don't trust their own system, we shouldn't either, and also following social etiquette – returning a disfavor, so to speak).
This site has been doing that for quite a while, and will do things like link to answers.com if we need WP's content for some odd reason.
Note also that WP's guidelines strongly discourage using blogs as a source . So, if you're a blogger who has a real news story you might have trouble getting your link to stick, and even if you do it will be nofollowed. And, as described here, that might result in WP ranking higher for something than the site with the original news.
This move may lead a small number of people to commit acts of vandalism against WP as a form of revenge, such as by attempting to stuff pages with spammy words. It might also lead to some people spamming not for (the apparently non-existent) "link juice" but for simple traffic. For instance, so far this month their Playstation 3 page supposedly got 40,000 views per day; a well-placed link there could result in hundreds or thousands of click-throughs.
And, it would be interesting to find out which links in Wikipedia don't have that tag; for instance, their links to the wikimediafoundation .org from their main page don't have nofollow.
On a technical note, this tag only seems to be added after a page is edited, perhaps due to caching. I originally thought I found a case of a link without the tag , but upon saving the section (without any changes), it had obtained that tag.
 Wrap these lines and remove the space before ".org":
 Remove the space before ".org": en.wikipedia .org/wiki/WP:V#SELF
 The link to cdc.gov here (remove the space before ".org"):
(Note: Placing links in that format is not necessarily suggested, that's just the method used in this instance.)