World-building isn't a new hobby; fantasy authors and tabletop GMs have been facing questions like this for years, and often throwaway comments cause a lot of trouble for those making film adaptations or video game versions of the world. Creating a world from scratch for gaming means that all the important questions need to be answered at once, however, or the players will ask them. It doesn't stop at the design stage; game companies are providing governments, too, by creating laws and rules on the fly.
Universes created primarily by users, like the world of Second Life, still operate within boundaries and constraints set down by the developers and providers of that world. If the Metaverse idea is really the future of online gaming, there's going to be a lot of influence exerted by some early decisions, just as early networking protocols and standards still influence today's Internet.