There are a lot of dark marketplaces but it will not be a problem for the bitcoin and dark marketplaces will always stay alive....
I disagree, I think the dark market will make the image of Bitcoin be bad for people.
Dark places are not bad for bitcoin, everything without banks control can be called dark..This leads us to basics of liberty and freedom so yes why not? , Bitcoin was made for use without control..
Not only bitcoins have dark marketplaces but also in real world with fiat money they have also dark marketplaces.
As long as there is money involve per transaction dark marketplaces will exist.