Virtual Worlds will reach one billion users in 10 years.
OK, I'll buy that, but why?
In most measurable ways, virtual worlds are simply a new wrapper for chat and game rooms that have existed on the web for years? Sure, the new 3d interfaces look more like traditional video games (Sims, World of Warcraft, etc.) but those games aren't anything new, either. What's so new and interesting that somebody would predict a billion people will check them out?
Marketing - Virtual Worlds provide unique marketing opportunities. Smaller (or less aggressive) firms can buy sections or ads in existing independent worlds. They can sponsor games and memberships so users feel like the company is giving them something. More ambitious firms can build their own Virtual Worlds, and aggressively promote them. If going to coke.com means going to CokeWorld.com, that's a lot of people right there. Imagine Budweiser World...
Transformation of the Internet - There's a lot of talk regarding standards for virtual worlds so users can bounce from one to the other much like they bounce from one website to another now. If that happens, VW's will start to take over the role traditional websites have now, and that really would be a virtual world.
Getting It Right - There's a lot of VW's on the right track already. Once best practices are sorted out, the door will be wide open for anyone with a great idea to build a VW based on those practices plus established technology. I expect there to be at least some sort of standardized virtual world design tools before too long. It'll never be easy to build a VW, but if a designer doesn't have to reinvent the many wheels that make up a VW, what's left is manageable.