1) The potential for someone to fail at what they are appointed to do.
2) The predictable demise of a person or object.
3) The likelihood that a leader will not be powerful or head-strong enough to lead.
1) "The untrained Doctor has a high fallability factor"
2) "Steve Staunton's fallability far outweighs his managing potential"
3) "The new manager is a pussy thus he is the king of fallability"