Security option: explicit host/node permissions. I think this would be nice: When creating a new folder you could check this option. When adding this folder to another host, the source would get a notification that would need to be accepted manually in order to start syncing. The permission may be revoked later. For extra security the underlying implementation may use handshake ids instead of host ids to manage permissions. A handshake id would be generated every time you add an pre-existing folder to your host.
