The web has many problems, and lacks much of the functionality imagined by its conceptual but unimplemented predecessors like Vannevar Bush's Memex and Ted Nelson's Xanadu project. They also have only rudimentary ideas of where they've been and where they can go. Totally representational and totally abstract worlds both have their problems. Mcubed combines the best of both. Collaborative document creation with current interfaces is basically impossible.
Most people still print out pages and link in their changes with a red pen.
Media integration on a 2D page hardly makes sense, when even existing hardware is capable of more. 2D pages are a medium to be integrated, not a medium for integration. It makes more sense to have 2D objects in an intelligently designed 3D space than to have 3D objects inside 2D windows. It's exceeded its designed capacity. Writing software to deal with it is painful.