The problem is that that excuse can be used for anything. The obvious solution is to just use silkroad.

Using a marketplace, even if other people do illegal things there, does not make you a criminal. I buy things downtown all the time, some people buy drugs there, if proximity to crime was a crime, you are already guilty, get over it.

For the hyper paranoid: If buying/selling gold becomes criminal, then at least you are doing business somewhere that takes security seriously.