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...