Sure. You can absolutely replicate chunks. But you start kicking the problem upstream. A rack down is a couple pb, so you start doing a ton of cross rack transfers to get your replica counts back up. Now you're gated on nic/TOR/agg switch throughput. A DC down and you're gated on nics TORs Aggs & intra DC network. And this keeps adding up $$$ the further you get.
Ms had an interesting paper on data locality in storage last year. Can't recall the title offhand though.