@ted @thegibson it does seem that the network effects of federation cause content to surface in Google. Of course SEO outfits lack any sort of clue about the audience here or the point of federated services besides seeing instances surface in their data.
I've also witnessed a curious phenomenon on my server of "sleeper" accounts, which sign up but don't bother posting anything or even following anyone but me. Not sure what that accomplishes for them. Maybe relaying has something to do with it?