Large scale network partitioning can happen. Data center ingress/egress can go down. If you shard to multiple data centers, it's still possible for an entire autonomous system to have an interconnect with a different AS break. That is rare as hell with the actual Internet because of all the route redundancy even between ASes, but I've seen it happen on more specialized networks. For a few days last year, the entire western half of the US was cutoff from the eastern half on Raytheon's internal TS network because someone digging a hole somewhere accidentally cut the wrong fiber line.