Rebuilding something in a truly decentralized fashion (and it’s probably worth thinking about what that even means, exactly) will likely require approaching / building lots of things differently than we are used to. For instance, we would need to make sure we don’t run into the problem you mention where Bob ends up expected to pay for storage of old data. Perhaps we would have to relax the expectation from the outset that a fully fleshed out snapshot of the entire App Store must get backed up just bc Bob’s WoT likes it at that moment in time. If he wants to back the whole thing up, he could do that separately. Just like I may have a local list of the 1000 best rock songs of all time, per Rolling Stone; it doesn’t mean I necessarily have them all on my phone. But maybe I’ll use the WoT-curated list tomorrow to help me decide whether to purchase one.

(I hope I’m following your line of thought. Let me know if I’m misunderstanding!)