What obligations do neighbors have in hazard mitigation

This fascinating article in the New York Times is about how people in a coastal community in New Jersey are shaming neighbors into allowing the construction of a large sand dune in front of their property. The dune would protect property from storm surge. The problem is that the people who won't allow the dune to be built put other people in danger by refusing to allow the dune. They cannot be forced to allow it, but it appears that they are being coerced, and some of the holdouts are not happy.

This article raises so many interesting issues, including

• What is our obligation to the community to mitigate storm hazards in a legal system characterized by individual property rights?
• Why doesn't the government just exercise its powers of eminent domain to build the dune? (Because compensating people for such a "taking" is expensive)
• Why should the government be building hazard mitigation works, like a dune, or other such things such as groins, levees, and "hardened" beaches? Are these just subsidies to wealthy property owners? 

These are the sorts of tough questions that policy makers have to address when regulating land use in hazardous areas.