I disagree where you say 'an octree is definitely part of coding an MMO.' An Octree is just one technique to reduce the size of the Potentially Visible Set of

I disagree where you say 'an octree is definitely part of coding an MMO.' An Octree is just one technique to reduce the size of the Potentially Visible Set of geometry that is sent to the rendering pipeline. While its a quite a natural fit for a voxel-style world, such as minecraft, there are many techniques to achieve this; an octree just being one. If the Octree was the core technical challenge and data structure used to create every MMO, then I'd have no issue with the article. But its really not - its a simple technique, graphics 101, used to speed up rendering (or collision detection). Further, just having an octree is not nearly sufficient for handling MMO scale issues - a lot more needs to go into structuring the world - when those larger challenges are solved, I'd like to read his article on it.