Why I think this is relevant now and not earlier this week when DPR was arrested, is that law enforcement now have proven means and intent in unravelling Bitcoin transactions to follow criminal transactions.
Dread Pirate Roberts was arrested presumable by ordinary police forensics. Blockchain info was not used . Now it is!
First of all these are 8 sellers, not users. Second of all, I read somewhere that they were made within hours of DPR's arrest, so that all the sellers wouldn't start taking precautions. No blockchain is being used anyways, if that isn't enough proof though, all they're probably using is SR's site logs or something like that. And if they don't use BTC, they can easily peasily switch to something even more untraceable like Zerocoin, or, like they did, use tons of laundry addresses.