What happens if say 3 shards of a specific file you need are not online that day? Or never come back online again? I understand the files are copied to multiple locations but we are not talking about a 24/7 datacenter but random computers. People can decide to uninstall the program or never power back on or anything.

Unless it’s copied to basically every computer I don’t see how eventually someone would have a corrupted file just because they are unable to piece it back together with available computers.