It's also worth remembering that fires spread. If the house two doors down is on fire you better hope they and the house next door have insurance (and remembered to pay the bill this month).
You hit the nail on the head which naive interpretations of libertarian isolationism often miss -- unchecked problems spread viz fire, pollution, garbage, disease outbreaks, crime and poverty.
As one's liver combats the effects of pollution in your bloodstream by filtering it, so, as a society, we have developed certain organs to combat the degrading effects of similar sorts of problems.
