Originally Posted by BAMF

Basements are sometimes used to reduce settlement on a building. If the soil is compressible, they can use a basement to remove a volume of soil. In effect, this reduces the total weight of the house acting to consolidate the soil. If balanced exactly, the house+basement can actually float in the soil, and no settlement will occur. This only happens when the mass of the soil removed = mass of the house. The result is that the soil under the house has already compressed due to that mass, and no additional mass is applied, so no settlement occurs.

You will probably see more basements in poor soil areas, like clays/silts..near rivers, etc.. You will probably also see more basements were frost heave is a problem. If the basement of the house is below the frost line, then the house wont rise much when the ground water freezes. I think, I havent had anything to do with frost heave in a long time.