My experience and thinking about BOBs stems primarily from a couple of decades of fairly intensive SAR work in th highly variable climate of southern Arizona, so first of all, I would suggest that an effective BOB will need to be seasonally adjusted, at least for most of us. In southern Arizona, we faced temperatures ranging from -35F (at altitude in winter) to 108F (amid the cactus in summer). Since the SAR pack in the summer was essentially a giant water bottle, our winter packs were actually lighter.

Everyone's scenarios will be different, and the minimal contents of your pack should reflect the varying possibilities. Like Russ, in the case of wildfire, I will definitely bug out - I have actually had the car loaded and ready to go on two occasions already. In case of earthquake, my preference will be to bug in, at least initially.

Obviously, if circumstances permit, leaving in a vehicle is preferable. It certainly helps if you have looked at worst case scenarios and thought and packed for leaving on foot. For me,an attractive option would be BOOB (bugging out on bicycle - a lot more range than on foot, and not as restricted as a vehicle).

Basically, if you have the ten (or fourteen or so) essentials covered, you will probably be in business. And your pack will likely bear a striking resemblance to a backpacker's rig.