Let your customers do the job. When you're nothing but an empty shell, where can you get substance for a better price ? Google Earth was a really smart move to aggregate content and value but it takes time to build a virtual world... so why not ask your visitors to build their ownhomes ? See SK Telecom : an army of minimes designing their own environments and even paying for the virtual stuff they add (show me the acorns : cyworld's totoris) !
Google may not end up hammering down competitors with YouTube, they keep giving their users potentially dangerous tools and Google SketchUp, an easy-to-learn 3D modeling program, could turn as addictive as Earth or even Hell. For those who tend to plan ahead at least. Probably not the kill app for the masses, but one for a rather interesting target for announcers.