What bothers me about people's using these locks is that it seems, if someone with substandard morals were to get ahold of the master "key," wouldn't these locks become prime targets?

I realize this is based on two assumptions:
1) A thief (or group of thieves) is organized enough to obtain a key (not a spur of the moment petty thief)
2) These locks become prevalent enough to make it worthwhile to obtain the key

I'm not sure the second assumption is a reality at this point, so it probably doesn't matter. The locks are still better than nothing, I suppose.