Somehow this Windows Rights Management thing recently announced by Microsoft slipped by me last month. This article from Cover Pages does an excellent job at explaining what its all about.
The RMS technology uses “tested and proven security technologies, including encryption, digital certificates, and authentication. Putting persistent protections in the documents themselves helps customers control and protect digital information both online and offline, inside and outside the perimeter of the firewall. Because Rights Management policy expressions can remain within files during and after transit, rather than residing on a corporate network, usage policies can be enforced even when rights-managed information leaves the network. Policies can be used to control forwarding, copying and printing, as well as establishing time-based expiration rules. Permissions can be set to expire at a specific point in time, such as a number of days after publishing or at regular intervals, requiring acquisition of a new license.