Reddit wasn't initially different though is my point -- it wasn't publicly traded, it had trickles of users initially, and didn't have adverts. Hell, it popularized the canary reporting as part of its yearly ethics report.
Some feddit instances are more popular than others, and once they gain traction amongst the masses, might be rife for viral media targeting. Yes, the defederated architecture in theory prevents against that, but if one server swallows up all the users by offering something the others can't, then that somewhat easy balance between instances might get upset
Who knows what the future holds, but we've seen what happened to other sites and it would be epitome of hubris to believe it couldn't happen here