When it is clearly obvious that it is a mutual collaboration between MN and the DM?
I came across an article about a MN thread and there were several links to the thread along with a 'read the full story here' link at the bottom of the page. The article is obviously intended to drive more readers to MN and is basically a big advert for the site.
MN may not be as big a site as the DM but I'm pretty sure they could tell them to back off if they didnt want their stuff poached on a regular basis , especially as its obviously upsetting a large portion of their readers. MN also never comment on any threads relating to the topic which makes me think they may be in cahoots.