I've never had to make the "call of shame" and get someone to fetch me on a commute. However, I did have to walk 3.5 miles in my cycling shoes one day when my rear tire repeatedly flatted and I ran out of CO2 cartridges. I started carrying a pump and tube repair kit after that -- in addition to a spare tube and CO2. On a number of occasions I have caught rides home with coworkers and left my bike at work when severe thunderstorms popped up in the afternoon. There's no way I'm going to ride 16 miles in a severe storm if I can help it.