I.E. it is already being actively used to launder money.
Laundering isn't particularly difficult anyway. You're probably still just better off buying a bar and pouring vodka down the drain.
#1 get the money into bitcoin. How did you get it there in substantial quantity to begin with? There may be $100m of it in supply but how many people have a hundred k bitcoins they will readily exchange for cash? It has to be cash, if you put the money in a bank it's easily traced and therefore pointless.
#2 get the money out of bitcoin in such a way that you can pay taxes on it. Since you presumably can't buy houses, cars, or jet skis with bitcoin it's not very useful there. Even if you could buy a house or car, you'd still need to file taxes since the government can easily see that you bought a $500k house while claiming 0 income. The whole point of laundering money is to pay taxes on illegally gained cash so you can spend it. (Tax evasion is its own separate crime and industry, and I suspect bitcoin isn't very useful there either.)
So now you have to start a shell business that you can claim made all of those proceeds in bitcoin. It has to be one that doesn't legally require you to KYC (banking industry slang, meaning gather relevant info about the people you do business with) and report to the IRS. Then you have to find people to buy the hundreds of thousands of bitcoins from you.
Far easier to start a bar, buy alcohol, pour it down the drain, and claim you sold it. If I were laundering a few hundred grand a year I wouldn't waste time on bitcoin.
You have to transfer them from a bank account, right?
Even if you got the money in without being traced and spent them that's not laundering, it's tax evasion.
Back to the article, like another poster said, how is a bitcoin-based drug site any different in terms of anonymity than a cash-based one if you have to give your address out at the end anyway?
The idea, in theory, is that the use of BitCoins cannot be tracked by a third party. That is to say, Silk Road, you and your dealer are the only ones who know about the purchase. In theory all three of you do not keep records of the sale, unlike credit card companies, which keep records of EVERYTHING.