First, this is explicitly unclaimed stuff; any who had a (in their mind) legitimate claim on those bitcoins had an option to claim [part of] them as their property; apparently noone did.
And if it's the property of Silk Road, then no matter what their deal was with the users, when it closes shop then the due process generally doesn't involve giving parts of their assets to users or creditors - the due process is to auction off those assets (as they're doing now) and settle those liabilities with US dollars; so again, people can claim that Silk Road owes them bitcoins, and they can get paid an appropriate share of this sale.
And if it's the property of Silk Road, then no matter what their deal was with the users, when it closes shop then the due process generally doesn't involve giving parts of their assets to users or creditors - the due process is to auction off those assets (as they're doing now) and settle those liabilities with US dollars; so again, people can claim that Silk Road owes them bitcoins, and they can get paid an appropriate share of this sale.