There are adding more and more from this kind of dark marketplaces and some are pretty interesting but its depending on what kind of goods, there are also a lot of scammers that is the downside.
Yep they are growing and this is because everyone wants to be more anonymous than back in the days what is good but also can turn into bad things.
Anonymous is good but if everything is doing this it will be very dangerous for us all, I think that dark marketplaces are indeed good but can be bad if you think about other persons that want to harm someone.