And how did it work with the Silk Road?
Scamming was rife, but largely mitigated by the fact that the dealer cant effect their reviews and nor can the buyer. The dealer has the choice to not sell to you based on your history, the buyer has the choice to not buy from a dealer with a bad history.
Other than that, bitcoin had little to do with its security apart from providing anonymity. If it was possible to do so anonymously you could have just post them cash.