Title pretty much says it all. Doesn't matter how many "temporary Bitcoin addresses" they generate or what fancy features they flash in your face (wow, such tumbler!).
Any marketplace with on-site escrow should be treated as compromised. There is no longer any excuse. We have the technology for easy multisig transaction integration and there are also legitimate clearnet BTC escrow services available. If you wouldn't store coins on site why keep them in escrow on site?
Normally I try to reserve this account for posting things of a much less obvious nature but I would have thought people would learn this after SR1, Atlantis, and Sheep. Going back to the same tired old paradigm isn't going to cut it anymore folks.
Edit: Right now this means Agora, Blue Sky, Pandora, FloMarket, Tortuga and probably others. Do not use these. Seriously. The last two times I challenged someone in this community on security related issues it was Sheep and Tor Market. I haven't looked into any of the markets I listed beyond their front pages but my initial opinion is that these are not well engineered or well put together projects. Vendors and buyers alike beware.
Edit 2: Added Tortuga to the list.
Thank you for being the one to say it. I've been shocked by the fact that people are willing to rush to these brand new sites knowing that more established markets that we thought we could trust have been dieing off left and right.
The only reason you should be using one of these sites is if you have a dependency to a drug that you can't get locally. Otherwise you have no excuse to be risking your money and freedom on these new sites. We are going through a rough patch here and the only way we are going to get through it is by adapting.
Be safe guys.