Upon saying that, I've added extra locks (bedroom locks) to the past 2 houses I've lived in, and the landlord had no issues, but that's student flats and cheap landlords.
That's not to mention that it's a lot easier to just break a window than pick a lock. I have never heard of a burglar breaking into a house by picking the lock. The sort of people that burgle residential houses tend not to be the sort of people with the skill, intelligence and finesse to pick locks.
