Common Voice is an amazing project. Here is an idea that might attract more voice samples and validators. I realize it might currently be a little out of scope.
English Language certification exams like IELTS, TOEFL, and the various Cambridge exams could be made much more effective and efficient by crowdsourcing the the listening and reading discrimination tasks that are at the root of these tests. The validation method for the Common Voice voice samples could be easily adapted into a more formal sample discrimination methodology like triangle testing. The validation system could be expanded from individual sentence samples to larger samples of conversation. English language testing is a mulit-billion dollar industry. An open-source, crowd-sourced alternative would attract a lot of interest, and help the 6 billion+ people who are non-native English speakers who much prove their English proficiency to access higher-education and skilled jobs around the world.
Thank you for your time, and thank you for starting Common Voice. I hope it has a lot of success.