The problem is that the current hardware will not support it and it is uncertain if the newer players hitting the market will.
In most cases you will need to upgrade any existing players and make sure you check on any new purchases to see if it supports the Managed Copy feature.
Read more here.

each studio is required to sign the recently finalized AACS license by December 4th 2009, and any studio that signs early receives up to a 25 percent discount on licensing fees. What isn't mandatory, though, is hardware support, and although the current generation of players definitely won't work, most expect the majority of new BD devices to. The cost (you didn't think it'd be free, did you?) and the number of copies is up to the studio, but at least one copy will be allowed. That copy can be made via a menu on the disc and can take the form of another Blu-ray Disc or a DRM-laced Microsoft file.