It's a good thing in this case they also don't have to worry too much about bad actors, since it's a fundamentally altruistic endeavor. Worst case scenarios: 1

It's a good thing in this case they also don't have to worry too much about bad actors, since it's a fundamentally altruistic endeavor. Worst case scenarios: 1) Someone keeps downloading the full archive and throwing away; 2) Someone wants a file erased, keeping it with the intention of denying access in some future. -- 1) Bandwidth has costs on both sides; just balancing upload among receivers would probably suffice for this not to be a problem. 2) Assigning large random chunks to downloaders should prevent this "chosen-block attack"; add in some global redundancy for good measure and that's probably enough (although I still wouldn't trust this 100% as a primary storage, only as an insurance storage).