I'm shocked that the question in this post was never answered:
Quote Originally Posted by theroobs
... I need to buy a 256mb card and not sure what this means:
Cryptographic security for copyrighted data based on proven security concepts from DVD audio
I see it on every description of an SD card - what does it mean?
I'm even more shocked at how few hits there were when searching the Internet for a straight answer, considering this technology has been around for at least 4 years.

I found some info, here it is.

(1) CNetAsia article:
(2) SD Association - Content Protection for Recordable Media
http://www.sdcard.org/sd_memorycard/images/img05.gif

Based on this diagram if you copy files with DRM (Digital Rights Management) or some other copy protection scheme from one SDc to another SDc with the same security feature, then the copy will fail.