Hosting your Social Media Accounts (or not)
Federation
Federation is just great. It means that if you don't like existing servers, you can just run your own. It's not like Facebook or Twitter, where there is exactly one provider, and if they don't like you, you're doomed. It's just like email! (... well, if we ignore the fact that somehow everyone seems to be using gmail these days. At least corporate email addresses are still a thing!)
Except... well, running an email server is... not for the faint of heart. I did try doing it at some point; it's fun for a while if you set up DKIM and SPIF and all the fancy anti-spam measures properly, but... some stupid recipients are going to reject your mail regardless. Also, do you really trust your security more than that of a company who has entire teams of dedicated security people?
Your Mastodon / Pleroma server is probably going to contain fewer pieces of important-to-secure information, but... hosting them is still actual work. Doesn't it make sense to just pick a server you like and make a profile there?
Identity
But then... once you have a bunch of followers and you decide to move to another server... well, you have to convince all your followers to follow that account, too. Which is definitely a switching cost.
Email has this nicely solved, with MX records. Actually, XMPP has this nicely solved, too, in similar ways, via DNS! Meanwhile, for ActivityPub, it's still a debate whether and how this should be done. That is, you should be able to just point people at your own domain while enjoying the benefits of using a server hosted by someone else.
It's not really just a theoretical question either: I've definitely seen many people moving between accounts. Although, technically, you can set up basically a redirect page on your old server, but... it's definitely not as seamless as with email.
I haven't looked into the technical side of the above debate yet, but... it's at least a good thing that it's happening at some point!
... comments welcome, either in email or on the (eventual) Mastodon post on Fosstodon.