E-waste is just one of the problems, probably the only one most users could understand; but security is also a huge one. With apps requiring permission to essentially everything (and users surrendering them blindly) security on any mobile device as of today is a myth. Open Source apps could mitigate the problem by swapping an unreliable layer with a trustworthy one, but we still have closed device drivers which could contain whatever their manufacturer (or its government) wants without any chance of being audited.