Replication and fsync

I'm running 9.1 with a slave using streaming replication. A coworker wants to turn off fsync on the master and insists that the slave will still be in a usable state if there is a failure on the master. We all know that turning off fsync is a bad idea, but I was under the impression that the fsync setting would be replicated to the slave, making it useless as a backup in this scenario. Am I wrong? If I'm wrong, is there still danger to the slave in this kind of setup? Can I count on it remaining unharmed if the master suffers unrecoverable corruption?