A good place to make an in person trade would be at an airport. I doubt anyone would pull any kind of funny stuff there.
I doubt someone wouldn't. Airport security is a fucking joke. They wouldn't even need to bring a weapon, just scream "he said he had a bomb!", grab your smartphone, and run while all hell breaks loose in their wake.
Very true...I could see that happening. I guess the best way to trade in person would be, to go to a Police Station/Headquarters(with a lot of police present), explain to them what you're going to do, and then do the trade with the other guy.
OR
Hire your own bodyguards and do the trade with all 30 of them carrying assault rifles present. That should stop any mugging from happening.