> … users of one of … Google …? If that's the case, you don't need to as the key is automagically saved by your OS' platform and synced with your new device.

This absolutely does not encourage confidence in me. We all know how easy it can be to get locked out of a Google account and have no way of getting back in unless you have enough clout to make a huge noise online so a human there pays attention instead of you being stuck in the 'ol support-bot-run-around loop. It doesn't happen often when you consider how many users there actually are out there, but the potential inconvenience is high enough that “fairly rare in the grand scheme of things” is still enough to be reason enough to be wary.