Updating SSH Keys Across an Environment

Most Linux environments with any number of servers uses keys to perform tasks from simple manual administration to gathering manifests, backing up config files across an environment, and really any kind of automation. Why? Because passwords are terrible things (how's that for indignant). Seriously though, despite the risks passwords present with minimum constraints not being appropriately set or enforced, at least passwords make authentication and semi-secure security accessible to people. Of course, keys are preferable, but not reachable for the general public. Enough about my philosophical ramblings about security though. I have several servers that I run (including this one) that all use keys almost exclusively for logins. Like passwords, keys should be cycled through frequently as well and if you have things set up right, that should be completely painless. Here's the script I wrote to bulk change passwords across my entire environment.