HBO turned on CGMS months ago
People in the blog world are up in arms that HBO will prevent fair use by disallowing copying of HBO content. In fact this has already happenened. In June 2004 HBO turned on CGMS-A which prevents you from (at least on Media Center) from burning HBO shows or playing them back on another machine (or even your same machine if you lose your license because you say reinstalled your OS).
Update 1: The Inquirer has a lengthy rant on this issue, Prepare to get screwed by digital rights management.
Update 2: Cory Doctorow, Why market-forces can’t correct DRM. Cory Doctorow also gave a well known talk on DRM at Microsoft.