I think it's a great idea for an experiment, but like you, I hope that there was some sort of screening process. I'm guessing that people had to apply, and hopefully they were given some guidelines on what was acceptable.

I'm also guessing that if someone totally insane somehow got approved and started spewing nonsense or vitriol, the organizers would remove them from the project.

Even so...it only takes one tweet to cause a huge amount of havoc. I haven't seen any other mentions of it, though, so maybe it's going well. I'd be interested to see what their ROI is. I wonder if tourism will go up?