But what I've never considered was this factor:
The studios will spend an extra $15 million on each film to make them work in 3-D. The enhanced graphics, as well as 3-D's resistance to piracy, make the format attractive and worth the additional cost, studio and theater executives said.
This is interesting. Assuming that the studios did not release a "normal", non-3D version, it would be unappealing to copy the 3D version for sale. Still, I don't see this happening, i.e. studious releasing only 3D version, so this won't be a major factor in the piracy fight.