I really have no idea what Pligg is about. Even after reading their about blurb on the site:

What is Pligg?. Pligg is Web 2.0 Content Management System (CMS) unlike any other existing CMS. Pligg's Web 2.0 user interface gives your visitors a reason to come back to your site by making them decide on the site's content and giving them the chance to social network. By giving users the ability to collaboratively submit and dismiss articles, you are offering an experience that users are happy to take part in on a daily basis.