Mastodon and long-term sustainability
One important difference between Mastodon and Twitter is that Mastodon doesn't have a business model. Mastodon is not a business. It's a microblogging software that runs on servers that connect to a federated network that, together, form the Mastodon network. A Mastodon server may be run for profit, but today most don't.
As a Mastodon user, you have access to the whole Mastodon network, but your profile and data reside on the Mastodon server where you created your account. If the people running the server decide to close down, you'll need to migrate your profile and data to another Mastodon instance. (Assuming they notify you in advance, that is.)
For example, this is from Fosstodon, the server where my account resides. They have given some thought about what happens if they decide to close doors:
One of the issues with a federated social network like Mastodon is users need to be sure their instance isn’t going to disappear overnight. This has happened a number of occasions we've seen, and we want to ease your mind in that regard should you choose Fosstodon.
(...) if we do decide to close the instance down, our commitment to you is that we will provide at least 3 months notice.
This should give our members enough time to find a new instance, migrate and ensure their followers know about it too. We hope that in the future a full migration option will be added to Mastodon, so users can fully migrate their accounts. In lieu of that process though, we will always do what we can to support our members.
Fosstodon also publishes each month how much they receive from donations, the costs of running the server, and how many months the server can run with current cash holdings.
Fosstodon's system administrators and moderators work for free. Thanks to the recent Twitter storm, the number of users on the service has grown from 20,000 to 50,000 in a couple of months. Their estimate is that each of them puts 4 hours per day into Fosstodon, aside from their families, day jobs, etc. They are discussing compensation for the team, because working for free is not going to be sustainable.
Mastodon adoption will continue growing, in part thanks to the recent Twitter storms. As the number of users grows, many Mastodon servers will see their hosting costs and admin time go up. They will need some way of paying the bills. Many will just close down.
These are the Wild West days for Mastodon. Take some time to understand who runs the server you use, how they pay the bills, and what their plan is in the long run if they have one.