The body of the article doesn't really refer to Bitcoin - but it's mentioned down in the 'How It Works' summary.
Officer's link to net drug market
* Two US senators have urged the United States Attorney-General to crack down on Silk Road and the digital currency that enables purchases on it, Bitcoins.
* Goods on Silk Road can only be bought using Bitcoin, an independent online currency.
* The peer-to-peer currency, which works via a piece of open-source software, aids anonymity on Silk Road because it is not linked to any institution.
* Bitcoin developer Jeff Garzik has previously said that because the currency log is public, it's possible that buyers could be tracked. "Attempting major illicit transactions with Bitcoin, given existing statistical analysis techniques deployed in the field by law enforcement, is pretty damned dumb," he told Gawker.com.
Another discussion thread:
"Silk Road Busted?" - https://bitcointalk.org/index.php?topic=92773.0