Spring in Bush's Afghanistan, and the Opium Poppies Have Never Bloomed in Such Record Numbers

Karlo at Swerveleft (hey, Karlo!) has lots of interesting material to ponder, including this:

The U.S. has been in Afghanistan now for years. And the accomplishments?

About 345,000 acres of poppies are believed to have been planted this year — an increase of up to 40 percent from 2005. The opium is refined into heroin before being smuggled out of the country to meet 90 percent of the world's supply.

In the same article, we find the following interesting comparison:

Afghanistan's drug traffickers have acted with virtual impunity since U.S.-led forces in 2001 ousted the Taliban, which in its last two years in power enforced a virtual ban on opium cultivation.

A ban? Why aren't the much more powerful U.S. forces banning the drug then?