If you are rich, why not? When sea level rise, increased frequency or intensity of bad storms, etc., makes it not worth living there...they can buy another house somewhere inland. Even if they have to completely write off the waterfront property, they should be reasonably OK.

It's the people who aren't rich who have to worry the most--the people that have most of their wealth tied up in their house, and so need to be able to sell it for a good price to afford to move.