And then there is the firefighter's perspective - SAAMI put out a great article on the safety of ammunition in a structure fire. Sure stored ammo cooks off, but it just goes pop, and nothing goes flying that a set of turnout gear won't protect you from - that's for ammo in a magazine or ammo in a box - now, if you have a round chambered, when it cooks off it leaves the barrel with at least the velocity that it was designed to have when it was fired intentionally.
I'm with Inspector Callahan on this one - if it is your only carry gun and you never leave it unattended, go ahead and keep it in condition one, but if there is a chance that it could be left in a house fire, please don't leave a round chambered - safety dictates a move to condition three.
Obviously this is just my opinion - but I don't leave the top cylinder of my revolvers loaded in the bedside lock-box for this very reason.
SC