Zinn: This is absolutely established in the books. Pipe-weed is something all the Hobbits abuse. Gandalf is smoking it constantly. You are correct when you point out that Middle Earth depends on pipe-weed in some crucial sense, but I think you may be overstating its importance. Clearly the war is not based only on the Shire's pipe-weed. Rohan and Gondor's unceasing hunger for war is a larger culprit, I would say.

Chomsky: But without the pipe-weed, Middle Earth would fall apart. Saruman is trying to break up Gandalf's pipe-weed ring. He's trying to divert it.

Zinn: Well, you know, it would be manifestly difficult to believe in magic rings unless everyone was high on pipe-weed. So it is in Gandalf's interest to keep Middle Earth hooked.

Chomsky: How do you think these wizards build gigantic towers and mighty fortresses? Where do they get the money? Keep in mind that I do not especially regard anyone, Saruman included, as an agent for progressivism. But obviously the pipe-weed operation that exists is the dominant influence in Middle Earth. It's not some ludicrous magical ring.

Noam Chomsky and Howard Zinn's unused DVD commentary for
Lord of the Rings (gotta love that McSweeneys)