You can use this marketplace (when it launches) just fine even if I was law enforcement. Use PGP, don't reveal personal information, use tails or VM isolation and keep your wits about you and you shouldn't have any problems.
God dammit I can't wait for the ability to dish out karma to arrive.
+1. More specifically, +1 to the first line:
"You can use this marketplace just fine even if I was law enforcement"
That's the whole point of Tor, of PGP, of tails and the rest...
Tor was never designed to stop LE from seeing the activity on it. Hell, it was developed for the most part by the fucking 'authorities'.
But the fact is, as long as you use it with a square head on your shoulders, it doesn't matter who's who and who's running what - you'll more than likely remain safe.