When talking to people whose objection to Bitcoin is illegal activity then Silk Road is only 2% of the Bitcoin economy.
When talking to people whose objection is that Bitcoin is all speculation and no commerce then Silk Road is 98% of the Bitcoin economy.
LOL.
It should be noted that not all users leave feedback. I have noted that with iPhone/Android apps maybe 1-10% of users leave feedback. Maybe with drugs it is a different thing, but I doubt it...
I would think that ratio is much higher on SR since the vendors rep are what customers look to when deciding what vendor to purchase from.
So the vendors want to get as many good feedbacks as possible, they often ask the customer to give feedback before the item has been delivered(!).
Still I dont think 100% of the customers leave feedback.