This is obviously stupid, buuut...  There is some truth to this.  Since every trader wants a margin, it's likely that each leg of a round trip of the silk road money is actually raising the price per coins, slightly.
The more something is useful, the more it's worth, the more interested society becomes, the more money people will pay for coins..

So it's the biggest exxageration I'll see today, but it's partially true, IMO