Of course, you are both correct here.
Spam was my first thought as well. Back in the golden age of blogging, I loved getting pingbacks on my posts, but the ecosystem became flooded with spam to the point that anybody old enough to remember what pingpacks are will automatically associate them with spam. It'd be nice if this service could address this concern, which lots of people will have immediately, and it appears they do via a plugin, as mentioned in another comment.
Since this is a centralized-ish service, it'd be good if they could perhaps address this at the hub-level.
