Hacker News pays close attention to the content on the main page. They purge anything that doesn't trend left leaning or counters the standard left's corporate interests.

For example, I posted a link to Michael Moore's film in which he eviscerates bio-fuels. This post was mysteriously removed. It was also removed the second time I posted it. This was despite the link the "A year wearing shorts to work" as another HN article link at the time continued to exist.