Federation can help if you run the software yourself since your identity and your "content" are tied to your instance just like they are with email. As long as you keep it running and make sure the software is up to date with current federation standards you're more or less safe from all those hazards. If the developers of Bookwyrm grow out of their anti-capitalist phase and sell it to Amazon, get that family and realise there is more to life than chasing characters on a screen, get hit by the proverbial Bus or otherwise lose interest in maintaining the project you still have your "content" and identity which you can keep alive by either federating with other ActivityPub-enabled platforms - which will probably lead to a loss of functionality - or maintaining/getting someone to maintain the project for as long as there are interested users. All this stands and falls with the viability of ActivityPub, it will be interesting to see whether the concept pans out in the coming years.