Wikipedia has taken a stand against 381 account owners who have been identified as “black hat” editors: effectively people who have been paid to promote specific pages on English Wikipedia.
Wikipedia has often been prone to this type of exploitation. In the early days it was a place where people would create pages about, and links to external sites in order to gain an SEO benefit. Wikipedia links were full “follow” and could really help push a site listing up the SERPs.
You can read the full statement regarding this issue on the Wikimedia blog.