Does this make any sense at all? How are 20,000 people going to collaborate on anything? Isn't the management nightmare -- even though I'm sure it's mostly done in software -- going to prohibit any real forward progress on a game like this?

Or is it just going to be a core team of 20 or so, sifting through 20,000 submitted texture maps?

What a weird idea. But whether it succeeds or fails, here we are again, exploring the unique potential of the Internet to service heretofore unheard of levels of collaboration.