Great analysis of Silk Road's historical impact on Bitcoin from The Genesis Block. This is illuminating:
[T]he complaint states that site’s total revenue between February 2011 and July 2013 was 9.5 million bitcoin. Over that same period approximately 225 million bitcoin were transacted over the block chain, of which the 9.5 million in Silk Road sales accounted for just 4%.
Is that big or small? Also, here is Felix Salmon with another good analysis:
On top of that, the numbers in the FBI complaint are highly misleading. The complaint says that Silk Road’s total revenue, of 9.5 million BTC, and commission, of 614,305 BTC, “are equivalent to roughly $1.2 billion in revenue and $79.8 million in commissions, at current Bitcoin exchange rates, although the value of Bitcoins has fluctuated greatly during the time period at issue”. That’s putting it mildly. ... [In June 2011, a 50 bitcoins were worth about $150, or $3 each.]
Those 50 bitcoins are part of the FBI’s 9.5 million BTC total, but rather than being worth $50, the FBI is now valuing them at about $6,300. As a result, the $1.2 billion number should be taken with a monster pinch of salt. Besides, if you consider that the FBI is looking at 898 days of Silk Road activity, that averages out at a pretty modest 10,600 BTC per day. That’s hardly the “underpinning” of the bitcoin market, which normally sees somewhere between 200,000 BTC and 400,000 BTC per day in total trading volume.