One of the biggest challenges with Second Life was the steep learning curve for learning how to build things. Sure, once you got the hang of it, it wasn't that bad. But it took a while to get the hang of it. So this led many users to kind of feel stuck after they ran out of things to do if they weren't willing to learn how to build things. Virtual Reality will probably have the same challenge, as just sitting and staring at stuff will get old fast. The Mozilla VR Team is already on a system that allows users to build VR content in a borwser, using existing browser tools (APIs, HTML, etc). One example of this is how the team built a Minecraft environment with the WebVR A-Frame kit. The magic of this A-Frame system is that it uses html code to build objects in virtual reality. You could write out your VR build in code if you wanted. But there are many other possibilities, including the ability to create applications that work on different devices.