It is a problem. Though I don’t know how big the problem is, but maybe it’s significant. That’s why I’m saying about community merging and replication in another comment to this post. We can divide the problem into two: having a backup in case of technical issues with the main instance, and community ownership / trust things. The first one is truly technical, the second one is about people and has no easy solution IMHO. What if the owner decides to kill the community entirely? Maybe that replication thing can help, one can set up a replica / mirror of a community even without notifying the owner, and that replica can become a reincarnated community instance once the original one is dropped. Not sure though how to backup user accounts in case of a dropped server with those accounts.