If you take a look at nimda and dooglus's post here...
https://bitcointalksearch.org/topic/m.1063869
You'll basically see that we know that the 1Dky address was owned by Silk Road. So we know they have coin, but we also know where it is from. It is possible that they needed pirate's LOANED coin to further complicate the process of where money was coming from and going to. Now that he's no longer an agent in their affairs, they are simply spinning off from the 1Dky address back to their vendors. This means the vendors are now responsible for "cleaning" their withdrawn coin.
For a practical application, expect to see at least a handful of high-profile drug busts over the next couple months, maybe. Large withdrawals from addresses linked to 1Dky are going to be pretty clear evidence of having a Silk Road vendor account.