OK so if I want to search for a newer equivalent of Silk Road, how do I go about it?
Thats stuff isn't going to show up in Google searches is it?
It does, you will find a few websites talking about it and you will have to choose to trust the URL they give you.
It's kind of like real life though, how did you get the URL of your bank? You either trust Google.com to give you the right one because you trust them as a search engine, or you pay a visit to your bank and ask them.
I think the only problem called out here is having Google Analytics scripts running on the page, which try to fingerprint the user's browser even when you're trying to search anonymously.