There is a stigma to monetizing your side projects. I take exception to this. Building useful software is hard work. Maintaining it takes even more work. Adding a revenue stream to a project helps make it sustainable. This is good for everyone involved.
This is a big issue in the open source community. Github and Google code are littered with the remains of half completed and unmaintained libraries. This is a loss to everyone involved: the volunteers that built the library, the brave souls who were early adopters, and the community at large. And when the open source ecosystem fails for a particular space, our end-users have no choice except to turn to a corporate provider.