Yes even Google is a user innovator: "The New York Times is running a breathless story about how
Google assembles the majority of the hardware it uses and deploys at such a large scale, that Google may be the world's fourth-largest maker of computer servers.
Users as innovators? Who would have thunk it? Actually Eric von Hippel, Karim Lakhani's thesis advisor, was the first scholar to point out that a majority of the functionally novel innovations arrive from users. His books "The Source of Innovation" and "Democratizing Innovation" (both available as free downloads) outline the basic thesis of users as innovators and and provide empirical data to show this effect.
NanoSummary: Users can be innovators because they directly experience the use environment with existing products and find them to be lacking in critical functionality. The decision then is to build or buy. Often times the buy option is simply not there because manufacturers do not experience the same use environment and it takes a long time for them to recognize the "need." Many advanced users cannot wait for the manufacturers to build something they do not understand or for marketing departments to agree that their need can serve the mass market. Thus they innovate. Its really that simple."