Through extortion and taxation, the Taliban are believed to reap as much as $300 million a year from Afghanistan’s opium trade, which now makes up 90 percent of the world’s total. That is enough, the Americans say, to sustain all of the Taliban’s military operations in southern Afghanistan for an entire year.
http://www.nytimes.com/2009/04/29/world/asia/29afghan.html?_r=1&th&emc=th
Not a chance of working. Oh sure -- it may put a huge crimp in the Taliban's operational effectiveness, but there are far more people making far more money off the poppy crops than simply the Taliban. What are these marines going to do -- guard the crops? The destruction of them is not an option.

The U.S. has been so successful with their own war on drugs.
Most successful. Why, in fact I don't think there's demand at all in the continental States for drugs anymore, is there? My recollection is that we're all just supposed to say "no", right?
If it worked for Nancy, it's gotta work for me.
"It is our decree that there will be no poppy cultivation. It is banned forever in this country," he said. "Whether we get assistance or not, poppy growing will never be allowed again in our country.
So you see people, the US did not INVADE Afghanistan. It was merely delivering international AID to the distraught farmers of that poor country.