As reported by Search Engine Land here, Wikipedia has put “no follow” tags on all it’s outbound links. Gray and Black hat SEO’s have been using Wiki to create “hot” inbound links to their sites that they are trying to promote. Even with all of the algorythm changes the search engines have made, inbound links from high ranking sites are still holding their stature. Since Wikipedia is a well traveled site, it just seems natural to promote a site via spamming links all over this “open source” site. So, once again, the site gets spammed and has to ruin it for others by putting a no follow tag on all links. What this means, is that when a crawler makes it’s way to a Wikipedia article, it will not grab the link and follow it to the site it’s linking to, rendering this “gray/black” hat SEO technique useless.