How many smoke detectors does it take?

Paranoid much? This high level of residential disaster prep is a little bit over the top. When I toured this cute little 2 bedroom, 1 bathroom East Sacramento home today, I couldn't help but wonder...why? Three. Separate. Smoke. Detectors. Over just one of the bedroom doors. The other bedroom door had zero smoke detectors. Was the occupant of that bedroom not as "important" as the occupant of this bedroom? Does each smoke detector work? Perhaps the seller couldn't figure out how to change the batteries and just installed new ones? But why install new ones without removing the old ones? Well...my buyer client opted not to make an offer on this one, so I suppose that the mystery of the smoke detectors will go unsolved.