Quote -JCM's in Posers native figures; You know how to rig? To Weight map and Bulge map? Then you do not need JCM's. Period. End of Story.

This isn't entirely true.

Weightmaps still have their limitations. 

You don't need as many JCMs as before, but they're still an important part of rigging that can fill in where weightmaps can't. Until weightmaps can be controlled via ERC and called up and removed on the fly, JCMs are still important. 

~Shane