When Facebook was just in its infancy, there was another massively influential social network that "everyone" seemed to be using. It was called Friends Reunited. Whatever happened to that? Facebook happened.
I hope Steemit becomes as popular as Facebook, but not as corporate. I think Steemit's strength is its decentralisation. That's what will give it longevity. The more centralised it becomes, the more limited its future will be – and I think the same goes for Facebook.