Should I be closing shops?

Their fault for doing that second chances thing that unbanned all the hackers that like to mess with the market like this.

I don't think second chance does anything... My falsely banned accounts were still banned after they announced it. Too lazy to send them tickets since they're too old accounts now.
Also, hackers will always hack regardless if their old accounts were released or not. Banning a hacker's account isn't going to stop them from hacking because people, you me and everyone else, can always make new accounts.
And for hackers, it's not hard to get back to their feet... unlike legit people, those that don't take advantages of anything, are the only ones that get hurt. And Nexon doesn't give 2 pomegranates about legits. (Take a look at their customer's support.)