Depends. Being a developer means you can also iterate lots of different ideas before finding the one that works. In that case development is 80% of the time. With today's tools (social, advertising, job outsourcing) the rest of the work can become trivial. I am now a believer that developers can be entrepreneurs and try to motivate former colleagues to do the same. Remember that recent article from M. Andreesen about software eating the world[1]? It's true.

[1] http://online.wsj.com/article/SB1000142405311190348090457651...