I'm not sure I agree with the objection to passwordless ssh keys. A system that uses passwordless ssh keys may be more secure than one using an unauthenticated protocol.
True. I guess it really depends on the data being transfered. I have not seen a case where remotely invoked rsync over ssh was necessary given the type of data it was. It's mostly a security thing. With passwordless ssh keys scattered around the network in use by cronjobs, the machines those keys can access are at somewhat more risk. If you run an rsync server to transfer the files, you know exactly how that can be accessed. With ssh keys, you have to ensure that, say, certain keys can only do certain things (which is more complex to setup and get right in the authorized keys file).
