Chairmain Hiro: Can a corp have more than 1 'Chairman Hiro' rezzed at the same time?
Chairman Hiro is a unique asset (there is a diamond next to the card name designating this status). While multiple unique cards may be installed simultaneously, only one may be rezzed at a time.
So, if you have two Chairman Hiro's installed, and one is rezzed and the runner runs on it, you could conceivably rez the second Hiro which would cause the first one to trash itself before the runner accesses it (so long as you do this during a legal paid ability window).
From the Android Netrunner rulebook:
Some cards have a unique symbol (◆) in front of their title. There can be only one unique card of the same title active at a time. If a card with a unique title becomes active, any other card that shares its title is immediately trashed. This trashing cannot be prevented.
Chairman Hiro has the diamond in front of his name, marking him as unique. You can have multiple copies installed at a given time, but you can't have more than one of those copies rezzed.