You know what would be nice? Making a "buy" offer; Telling people you want something. City trade is a nice idea and all, but me and my colleagues are never online simultaneously so telling them of what I want is pretty hard.
I can't believe how stupid I am. I do an entire playthrough just so I could get the last badge, then I decide to do the final boss for kicks before I get to the superbosses, and then I overwrite my save in the astral tunnel.