I mostly disagree with arguments to rationalize the sale of exploits, they create a massive power balance towards bad actors, but we have to be honest with ourselves, and like drugs, 0days are not going away.

Our only proper response is secure software development practices, employment of security reseachers, and adoption of security-centric practices in critical systems... such as the Linux kernel. Which is embarassingly not the case at the moment. For ex: http://unix.stackexchange.com/questions/59020/why-are-the-gr...