I intercepted an exchange about copyright infringement and movie downloading, the illegal kind.

Apparently its illegal to host torrent files, according to some pending court case's, but in this exchange a very interesting point is made:

I'll call them Bob and Doug.
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Bob:

You know about this movie. You know this movie is owned by its copyright owners. You know the upload of it to PirateBay was illegal.

Doug:

That's interesting. How exactly does one upload a complete movie to the PirateBay? Take your time, we'll wait.

Bob:

The whole point is that you don't upload to Pirate Bay, it is a search engine, like Google points to web pages (which may be copyright) but [snip] and shut down, how dare the give access to torrent links? and other copyright material?

Doug:

Good point. The media really does twist the scenario, don't they?

Bob:

It's not the media. The fact is MPAA/ RIAA don't want to piss-off google, and get all their links blocked, or re-directed to porn sites. [grin]

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And there you have it, the best explanation why MPAA/RIAA is against some copyright trading, but not anything else.