The MyDevices\Identity thing only meets one specific use case, which is unfortunate as it is pretty much forced upon you by Sync 2.0 Pro (unless you use multiple identities but then the licensing costs increase). As a raised during the beta, a better approach would be to have the concept of a device group - a device can belong to multiple groups. When you share a folder you can choose to share it with a particular device (or devices) or with a device group (or multiple device groups) or a mixture of both. However, I don't think they allowed the beta to run long enough to consider all of this.