Developer and author Rachel Kroll recently had kickstarter to fund development of a google reader replacement, which she named fred. She has just posted to her blog a response to the many comments "well why not just open source it?" She mentions a few points, and importantly reminds everyone that preparing software to be released into the wild as open source requires a whole bunch of work, which she would have to do for free.
Other than that, however, I think she misunderstands open source and how it works. She repeatedly states that she doesn't want to lose the ability to monetize her software - and that simply is irrelevant to open sourcing. If she were to release her software under a BSD or MIT license, she would still be 100% free to charge for distribution, access, support - all the normal things you charge for in software. Even if she chose to use the much more burdensome L/GPL, she would still be free to charge fees for licensing and distribution, she would just have more onerous conditions to live with. There is absolutely nothing stopping her from releasing the code as open source - and, quite possibly, to do so may actually encourage people to donate to another kickstarter. Open sourcing the results from her development would foster a sense of community ownership, and it would probably also speed development. In any event, whether or not software is open source is almost 100% irrelevant to whether you can charge for software.