It's one of those tricks that's not super well known but a decent few know it - The Ubuntu server installer will ask if you want to import your ssh keys from Github, for example, and there was a Show HN[1] with a cool trick[2] that took advantage of this information.

[1]https://news.ycombinator.com/item?id=10004678 [2]https://github.com/FiloSottile/whoami.filippo.io