1) Non-fact based information processing and filtering
Problem: In a dishonest intellectual climate where the common goal is to win rather than to learn, people tend to assign levels of importance to news and ideas based on how good of a weapon they serve for their viewpoint or their opposition's viewpoint. If it serves as a good weapon for the person's viewpoint it is held in high importance and shared with others, if it serves as a good weapon for the opposition it is either ignored or shared with others through derision and mockery.

Impact: With political correctness in particular it allows people to ignore problems that they want to suppress or that they are too guilty or ashamed to deal with honestly, problems that their opponents may have no trouble discussing and hence projecting influence onto public policy in greater measure. More broadly it lowers the quality of public discourse in relation to professional (think tank, lobbyist, and public relations industry) opinion, negatively impacting the public's ability to influence public policy.

2) Consciously allowing the media to manipulate and frame references in exchange for confirmation of personal biases
Problem: I'll start with an example. Here are two snippets from an article that was linked to by poemless in yesterday evening's open thread:

On the other side of the mainstream media political spectrum from the Journal is the Washington Post, whose Op-Ed page leans towards what you might call "Lieberman Democrats." You know, real leftie stuff. Because America has such a diverse and free press. So how does the Post's take on Putin's Russia differ from the Journal's? I won't keep you hanging, so here goes, the concluding paragraph to an August 23rd editorial: "The West relies on Russian energy supplies at its peril."

Then towards the bottom of the article:

In a poll released earlier this week, Bush's approval rating has soared--SOARED!-- to 44%, the highest in ages. Even more shocking, Americans no longer believe that the war in Iraq was a mistake. The Bertrand Russell theorem applies to us too: we're getting what we deserve.

When I read that poll this past Monday, I exploded in laughter. The absolute, pure gullibility of the American public is without limit, bottomless...

There is a claim in the first quote that the American press is a uniform propaganda machine, yet in the second quote, the author is taking their output at face value.

Internet discourse in particular is rife with this kind  of intellectual indifference (among other colorful metaphors I will refrain from sharing here). When people submit to the media's point of view, they are stuck within the media's framework for understanding current events. The media's framework, at a minimum, represents elite interests that are in broad opposition to the interests of the public.

Impact: Increased inability of the public to articulate its own interests in the voting both and when attempting to influence public policy.

3) Assuming that you are smarter than everyone else, or assuming that everyone else is dumber than you
Problem: For reasons I don't understand, most of the world's middle class assumes that the above is true.

Impact: Retardation in the quality and impact of information exchanged between members of the public. As this belief increases hostility between members of the public, it decreases their influence on fellow citizens vis a vis professionals in the government and the public relations industry, who have a strong grasp on the psychology of influence as it is their job to begin with. It also increases isolation between different social groups, impeding the ability to see common interests between groups.