[CharlesW]

> My concern is that I haven't seen much thought into the security implications.

You may find this interesting: https://indieweb.org/Vouch

[giantrobot]

That doesn't do anything to prevent the DDoS problem of pingbacks/trackbacks, if anything it makes it worse because checking the third party vouch address causes an amplification attack. As with most things on the Internet spammers and assholes have ruined *back systems.