I've spent a couple of evenings exploring There, and still don't know whether it'll be just huge or just a pictureque backlot with really cute chat-bubbles and conversation-gestures.

There is to Croquet as DisneyWorld is to, say, Stonehenge. There's a certain economic imperative which you just can't ignore - Julian Dibdell's article in Business2.0 gives a really good overview.

Jessica Hammer has a nice observation: "if you plop people down in an environment that's too open-ended, most of them won't enjoy themselves". Maybe that's true, but surely in the long run, scalability will win out.

Two aspects to scalability. One, as Alan Kay says of Croquet, "the key to the idea would be to have it be scalable, without requiring servers". Second, to not lay landmines for unwary users by encouraging them in unsustainable beliefs (privacy or ownership, for example).