Wales attributes Wikipedia's initiative to user consensus, echoing the sentiment expressed by Reddit, the initiator of the blackout.
Over the weekend, Boing Boing announced its participation in the blackout with a statement by Cory Doctorow:
Boing Boing could never co-exist with a SOPA world: we could not ever link to another website unless we were sure that no links to anything that infringes copyright appeared on that site. So in order to link to a URL on LiveJournal or WordPress or Twitter or Blogspot, we'd have to first confirm that no one had ever made an infringing link, anywhere on that site. Making one link would require checking millions (even tens of millions) of pages, just to be sure that we weren't in some way impinging on the ability of five Hollywood studios, four multinational record labels, and six global publishers to maximize their profit.
Wikipedia's endorsement of the anti-SOPA campaign lends mainstream credibility to the initiative. While Reddit and Boing Boing are both unquestionably enormous entities on the Internet, Wikipedia deftly outweighs both of them, thus ensuring widespread attention is brought to the controversial matter.
Incidentally, it is difficult to overlook the contrast between Wikipedia's reasoned SOPA Initiative page and the MPAA Blog and Rupert Murdoch's Twitter rantings. Looking at each end of the argument in such a manner provides a poignant summary of the difference between the two camps; highlighting the irrational, lashing arguments of the pro-SOPA community, and the reasoned community-endorsed opposition presented by the anti-SOPA community.