Some tests demonstrating a VDB fracturing system I developed in Houdini 12.5.
http://vimeo.com/73640727 [vimeo.com]
I've found it offers a lot more control, flexibility, and better results then the built-in VDB fracture SOP.
Every iteration of my system removes a fragment from the input geometry and converts it to separate piece. These fragments can be placed randomly, or they can be placed at the edge of the piece removed the previous iteration - this provides the “decay aggregation” effect seen in the 2nd and 3rd fracturing.