Should you ever assume IO to be deterministic? Hard drives can crash, they can be slow(especially magnetic). Networks can disconnect, become congested or have random interference.
This is amplified on the cloud, but it should also be well known by anyone that works with the cloud. These things are well documented, although I could see why you don't really look for it until you have issues with it.
I think the problem is that from your average application developer's point view - there's nothing that they can really do that they aren't already doing (unless they're blocking the main thread on disk IO, in which case they can do a little bit more).
This is amplified on the cloud, but it should also be well known by anyone that works with the cloud. These things are well documented, although I could see why you don't really look for it until you have issues with it.