I'm not suggesting there's any merit to any particular conspiracy theories, but Afghanistan is a key region in the oil industry, specifically for pipeline routes. If the Afghani government won't play ball with Western interests with a stake in moving oil from Central Asia to Asian markets, the story goes, then the US will presumably do what it takes to replace that government.

All the tinfoil you can handle: http://www.democraticunderground.com/discuss/duboard.php?az=...

Again, don't downvote the messenger, I don't agree or disagree with any of these theories personally.