I for one am very keen to see us use this system, if for no other reason than it leverages the existing visibility of the Creative Commons machine-readable licensing structure. The CC-Public Domain Mark is not actually doing anything new/different to the concept of the public domain and doesn't pretend to force PD from one jurisdiction to another. In fact, AFAICT, it is the first time Creative Commons have a "product" that isn't a copyright license. Public Domain, by definition, is an absence of copyright which is why they're calling it the PD Mark and not a license. As such, this is not an attempt to rebrand the public domain but an attempt to make overt expressions of it consistent, recognisable and machine-readable.
From what I hear (I'm here at the Europeana conference now where they are
officially launching the PDM tomorrow - as per the press release http://creativecommons.org/press-releases/entry/23755 ) CC were debating whether to use a logo that was "C-with-a-line-through-it" or the letters "PD". The concern about the former was that it could potentially look like an "anti-copyright" logo which is not the message that CC wants to send out. But, they ended up choosing it largely because Wikimedia has already made the image recognisable through templates like "PD-old" http://commons.wikimedia.org/wiki/Template:PD-old-75 So, we were involved in the creation of this Mark even though we didn't know it :-)
Not being a techie I'm not sure what would be required, if anything at all, but how difficult would it be for us to implement the machine-readable information provided by the PDM into commons so that our PD content is made findable by this schema?
-Liam
wittylama.com/blog Peace, love & metadata