It's kind of a shame that the way Spore was outlined to work that each player's planet is essentially read-only.
Maybe if there were a setting to allow changes to filter back, or a tool that allowed a user to view what changes other players had done and pick from the range of outcomes.
It could be murder on bandwidth, though.
I wonder how well the DS can interface with the PC planet variants. Perhaps the DS only gets single planetoids/moons?