I say report it.  As you have described it it is more than just a mistake. 

Its time for our industry to help police these issues and stop being nice to the guys doing this type of work. They are costing us money and reputation.

Yes Spud, i think you should, its wrong, you know it and you have made the customer aware too.
its never going to be nice but you have to do the right thing or you wont be able to sleep at night.
Thats my thoughts

Yes definitely, this is not just a few clips missing, or even under pipe sizing, but a serious life threatening situation.  Plumbers are responsible "for the health of the nation" and here is a real example of that.  It's not dobbing, it's about who ever did this work never doing something like this again.  I assume you know the plumber, or at least who he/she is?  The owner can also make the complaint if you prefer, but I agree with Watchdog - we need to stand up and be willing to stamp out bad workmanship which causes risks to life and limb.  This person clearly does not understand the implications of what they have done.   Let us know how you get on.

I would suggest not to call this person a Plumber as they are clearly not.
 And as for reporting to the plumbing police I would have no hesitation knowing full well that i have done the right thing, remember you do have a professional responsibility to protect the health and safety of the public.
 if you feel that you are dobbing them in i would just draw attention to the job and let others decide the course of action.
 

Hi robbo
We are allegedly leading health professionals after all, perhaps we should be paid the same! nice pay if you can get it eh.
And as a side note are surgeons responsible for the materials they use to be fit for purpose?