While I think any action taken against OPEC would probably be warranted, I think that as a whole cartels are ignored in the US.  The MPAA and RIAA act to set prices for the media they control, yet rather than being shot down or legal action being taken against them they are ignored or even supported in the US.  In this modern era, trust busting is seen as anti-business and is pursued on a very small scale.  Mergers between very large businesses are often approved without any serious thought on how it will affect the competitive environment; anti-trust suits (such as the one against Microsoft) often produce minimal results that act as mere taxes against such corporate behemoths.

I'm kind of a Bull Moose, admittedly.  I believe that many of our political and social issues come down to overpowerful businesses, and vigorous action against them is necessary.  

The real question to me, is whether any party is at the point where they truly recognize these problems or even whether any government or group of governments is willing to act forcefully enough.  We have come a point where this is an issue, and most media ignores it, like the proverbial elephant.  If Mr. Noah and Slate are really interested in this issue, I would love to see a series on it.  One article on OPEC is a start, but if that's the extent of Mr. Noah or Slate's interest, it's hardly much of a position.  If free trade is really that good, it needs support all the way.