i've been able to trigger StackDepthErrors with significantly sized documents which make use of embedded callbacks. see

http://s3.amazonaws.com/drawohara.com.downloads/fail.tgz

for an example. it's very hard to tigger, so sorry for example size. (see a.rb)

this commit passes all tests and fixes the issue above. in summary there simply don't need to be two recursive tree walks: cascadable_children already recurses so we just don't need run_cascading_callbacks