The same holds true for monoliths like Reddit and Facebook and Twitter. What if they decide to just turn it off? In those cases you just lose everything. Period. With the Fediverse, if one instance turns off, then we just lose the stuff on that single instance. Everything else you have been following or doing is still there.
By and large, though, Fediverse instance operators are a communicative lot. If things are going to go south and the instance is going to go away, my experience has been they'll give you plenty of warning to move elsewhere and work to preserve whatever data you would like to keep.
The same holds true for monoliths like Reddit and Facebook and Twitter. What if they decide to just turn it off? In those cases you just lose everything. Period. With the Fediverse, if one instance turns off, then we just lose the stuff on that single instance. Everything else you have been following or doing is still there.
By and large, though, Fediverse instance operators are a communicative lot. If things are going to go south and the instance is going to go away, my experience has been they'll give you plenty of warning to move elsewhere and work to preserve whatever data you would like to keep.