Here's Renee Burton's (at Infoblox) comment on Philippe Caturegli's post on LinkedIn:

"When we contacted DNS providers about sitting ducks attacks ONGOING in their network via lame delegation... some responded with aggression and others with ambivalence. no criminals were disrupted and it was a waste of our resources even though it was the right thing to do."

And I can personally vouch that's mostly my experience and expectation as well, and not just for DNS issues.