I think it's pretty much impossible to run that kind of a global darkmarket otherwise. Even if you were the world's most experienced sysadmin and could lock down your server(s) (and NSA/FBI httpd/nginx/apache 0day doesn't apply) you still have to worry about Bitcoin laundering and many other issues, you'd have to run around like Jason Bourne everyday and nobody can sustain that discipline without making mistakes. You only have to make one mistake and you're joining Ross at ADX Florence (where he's likely going, nobody convicted of the "Kingpin" charge ends up anywhere else besides supermax prisons)
However, that would not be so easy for hundreds or thousands of Bitcoins. It's hard for a snake to discreetly swallow a pig. Numerous wallets and small transactions would be prudent. But the process could probably be automated.