[willvarfar]

3D spatial problems are just three dimensions. True you can do that with VP but you can do that with octtree too.

Imagine beyond 3D like clustering of friends or likes or recommendations or all those other N-dimensional data-points and you'll see the overlap.

[joshu]

Right. There are plenty of cases where you ONLY have the distance (or similarity) between two points and don't actually have an n-dimensional point in space.