I really hate when I hear 'there is no such thing as an unloaded gun" and "all guns are loaded." Good principles to live by until you verify other wise? Definitely!!! Any gun I encounter is checked as clear before any further interaction and will be once again any time it is picked up thereafter, but guess what.... while it is in my hands and i have verified it is clear the thing is unloaded, otherwise I could never clean it, dry fire it, check the bore, and I definitely couldnt/wouldnt hand it to someone who is new to guns to examine after my instruction.
Does that mean you should be careless with an UNLOADED gun? Hell no! It means you should be responsible regardless of loaded status.
As to the rubber bands you speak of, I dont see a point. In fact, it seems like an incredibly horrible idea, but then again, so does any locking system designed to be used with a loaded gun. Last I checked, I am not likely to have ample time to disengage some sort of locking mechanism (not speaking of integral safeties on a gun) in the event I need a gun.