The fact that mastodon apparently doesn't scale well could be a feature rather than a bug. You probably don't want thousands of users on a single server, since that brings with it all sorts of problems - social, technical, economic.
@bob I think it's interesting that it can sort of bring the social contract back into social media to have a federation.
I'm planning on starting my own instance when I have some money, then I can host friends and family on it. Spam and vitriol won't even be a concern.
My worry about technical issues is what happens to the horizontal scalability when there's hundreds of thousands of instances all trying to keep up with eachother?