It's probably worth mentioning that my thoughts on this matter are informed by experiences in driving crappy cars, living situations that have demanded substantial self-sufficiency, and enjoying walking and running.
In the past couple of years I've walked home three times. Once was well-prepared. Had my gear in the car, had stroller in the car, was picking up kids at preschool/daycare, and the serpentine belt snapped. Walked home, about seven miles. Supplies came in handy, especially spare socks, water, and the stroller I keep in my car. Kids mostly enjoyed it--although there were a few moments of "suck it up and walk kid," they also took turns riding on my shoulders when they got tired. Once could have been well-prepared, but I was too pissed off. New Year's Eve 2011, car battery drained while I sat in the car playing video games and avoiding going home. Instead of swapping out my coat for the fleece I had in the car, I ended up carrying the coat for the better part of six miles, along with a purse. That was stupid, because it seriously undermined my whole "I'm just out for a run" combination of look and attitude, but I had everything I needed. Third time was...complicated. To skip a long, boring story, I walked about twelve miles home, between evening and early morning, across most of town, in heels. While five or six months pregnant. That sucked. A lot. Enough to convince me to keep some good shoes and socks in the car pretty much all the time.