Good question! *Does* the publisher have to be in sync with the subscriber before replication can begin?
In my case, I have a publisher and subscriber who are (very) out of sync, and I was hoping to use replication to get them in sync. The publisher has some records the subscriber does not, the subscriber has some records the publisher does not, and they both have some records in common. Using merge replication, I was hoping that the subscriber's new records would go up to the publisher, the publisher's new records would come down to the subscriber, and that no records would be lost. Is this do-able with merge replication?