So when you tumble your coins you get someone else' coins, can't they trace the coins back to that person? who originally tried to tumble their coins but now are linked to your darknetmarket activies? Aren't all bitcoins traceable back to someone?
What if I sold some bitcoin and the guy who bought them used them for DNM purchases? Would I be a target of investigation?
It's not one person. When you tumble your coins your coins get split up and sent around. It's several people's coins becoming yours.