"Nothing free can be valuable" say some critics. That is, giving away things devalues them. This is obviously untrue in the digital realm, but what about physical things? The fear of the free was especially an issue in charity. If, with good intentions, you give medicines, or pumps, or solar panels, to the needed for free, won't they neglect, or trade off, or ignore these gifts? In particular, if you give long-lasting insecticide-impregnated mosquito nets to families in malaria territory, would they just use them for fishing, or sell them? Maybe you should sell them the nets originally for a small amount?
Turns out after many years of testing, that the free nets are incredibly effective in reducing malaria. Free wins! The story by Jeffery Sachs is here in Scientific American. Or you can read the PDF for the academic paper on the experiment.
Free or not, nets are a great idea and better than malarial drugs. If you want to fund a net ($10), there's a number of places that help you do that, including Nothing But Nets.