Antonin Pribetic offers information on online defamation from the AdviceScene.com Canadian legal forum:

"Anyone who republishes a defamatory statement, or facilitates its publication to the public (electronic or otherwise), may be liable for per se damages for injury to reputation ( and subject to an injunction (a court order enjoining or prohibiting continued republication, such as ordering a webmaster to remove the alleged defamatory postings) and adverse cost consequences..."

Entire article: http://advicescene.com/canadian-legal-forum/index.php/topic,532.0.html