They said the purpose of using a .json file was so that your configuration could be synced by dropbox or some other cloud service. I would NOT put my .ssh with all my private keys on dropbox.
Symlink'ing a ssh config file with Dropbox was the best decision I've made in a long time.
Same config file no matter which PC I am using, and you can always look up the IP/Hostname and which key it uses (don't store keys on dropbox for "critical" systems) through the dropbox web interface.
