Broadening the idea of a CTO from startups to companies with long track records, I've always thought of ideal CTOs as those who can balance risk and stability,

Broadening the idea of a CTO from startups to companies with long track records, I've always thought of ideal CTOs as those who can balance risk and stability, growth and retention. They are elastic enough to handle being stretched between the business/product/finance goals of the organization and the engineering required to make the product actually go. Good CTOs know about all the shiny new things but have the good taste to apply them only when appropriate, can manage the finances of an engineering team, and aren't afraid to hire developers who might be smarter and better than themselves.