Ok, more simply, what about a network partition where the redis machine gets cut off from the RabbitMQ servers?
My only point is really just that redis-as-a-queue has some bad failure modes if you aren't careful.
Sure, I agree and I understand things go wrong, so we've monitoring tools (munin, pingdom, pagerduty etc.) and we check them often or they post notifications often. There are at least two folks on-call 24x7. Based on present workloads we've calculations on how much time it would take to exhaust resources and we plan our servers accordingly, this buys us time to react.