The implication derived from a trivial probability argument is misleading. Failures are correlated, so 1-(1-P)^n is an upper bound, firstly, but secondly and much more importantly, the value being computed is the wrong value. Failure of a node is not partition. To non-trivially partition a cluster of N nodes requires (N-2) failures, when the cluster is fully connected, for example (as e.g. on any bus network). Handling trival partition is, well, trivial, in some important senses.