Fire will be an issue everywhere, but especially in densely populated areas where it can spread. In colonial times fires were pretty commonplace given homes had open fireplaces going year round, and construction techniques were only as good as the builder.
I’m not sure that Ferguson actually tells us anything new. Its a good reminder perhaps, but it is not an anomaly. The urban underclass reacts violently to perceived grievances, and they have absolutely no respect for anyone that isn’t them nor anyone’s property. On a smaller scale it plays out every day with shootings and other crime. That culture should concern us all because as soon as Uncle Sugar isn’t there feeding them, they will just start taking whatever it is they want and will do it in a way that fouls their own nest so to speak. Burning their local businesses in Ferguson isn’t going to result in more shopping choices nor better prices. In a SHTF scenario, it means they’ll fan out further and further to meet their needs. They are not going to focus on community gardens or other self sufficiency endeavors. That’s not part of the urban underclass culture. This is why urban survival will for most people be far harder than would be the case in rural settings.