In a way, it could be interpreted as very efficient. Only the branches where some "measurement" is done are "calculated". I suppose the others are garbage collected at the end of time, or something like that.
And maybe it's not a tree, but a graph of universes. In the same way that a universe split in two, two universe could also fuse into one when they share the previous state. Somehow it feels like this have to be connected to reversible vs. non-reversible computation.
Ah.. it's a good feeling being a fearless dilettante.
