Most people just download the Tor bundle and then access the Hidden Wiki.

Silk Road got shut down, and a few months back the FBI or some other government agency took down one of the owners of the hosting services/servers known for child porn, and they injected malware onto the users who didn't have their browser properly set if they visited those child porn sites.

Drugs sales and child porn were/are rampant, but I don't really buy into the assassin black market. Then again I've never really delved that deep into it.