While I'm sympathetic to the mindset behind this post (ie, by wary of git centralization), I think that (for example) issue storage is an orthogonal issue from

While I'm sympathetic to the mindset behind this post (ie, by wary of git centralization), I think that (for example) issue storage is an orthogonal issue from issue format. With a standardized issue format, it could be stored in a database or git, and as long as the service had an open export function, it would require no lock-in. Also, as some have pointed out here, storing highly relational data like issues and connected profiles, etc, could be an exercise in frustration if you tried to store all that in git. At the very least, it would be limiting.