Arccoss is one example. If you want further information beyond what I'm posting here, perhaps someone else will assist you. I'm not going to get into further detail.
from http://en.wikipedia.org/wiki/ARccOS (not that I advocate using wiki definitions as a reference, but this will suffice)
"ARccOS is an encryption system developed by Sony used on some DVDs. Designed as an form additional copy protection, it is used in conjunction with Content-scrambling system (CSS). The system deliberately creates a number of sectors on the DVD with corrupted data that causes DVD copying software to produce errors. Normal DVD players do not ever read these sectors since they follow a set of instructions encoded on the disc telling them skip it. Less sophisticated DVD ripping programs do not follow these instructions but try to read every sector on the disk sequentially, including the bad ones."
Anyway, checking off "Copy Protection Based on Structural Errors" in Anydvd's DVD tab (under "Feature Removal") works well when using Shrink, but, in my experience, very poorly, so far, when using Recode.