It's hard to keep up with all the goal post shifting (the definition of "product", "successful", and so on) - in any case, it's common for companies to start with the problem of delivering user value first, and then figuring out revenue later. One doesn't need a clear plan for revenue when starting out. The project I worked on at Mozilla itself is evidence of this: we had ideas for how to generate revenue for it when we started out, but the one we ended up doing was not on the list since we discovered the opportunity in the process of developing the product.