IMHO:
1. This is a recreational diver. Not a dive captain, DIR diver, or equipment technician. Most recreational divers rely heavily on shops to maintain their equipment and pay handsomely to do so. This should not have happened so soon after a servicing (unless the diver messed with it and the diver says he did not). But, regretably and uncommonly it does. That's when the shop must show its business acumen. Yes, I believe all recreational divers should be adept in checking life support equipment carefully and I try to impart that to them when I teach. However, even if taught, many divers get in the water too infrequently and leave important lessons on the classroom floor. That is why I support frequent local diving to keep skills fresh. But that was another thread involving same LDS.
2. Divers' demands were reasonable, regardless of who was at fault. He was not discussing lawsuit, he was not discussing liability. He just wanted a full refund for service he felt was not rendered. I am sure this has turned into a far more expensive issue than that of a standard regulator service.
3. In 22 years of diving, 3200+ dives, I have never had a second stage simply fall off the regulator. I've traveled in a lot planes, trains and automobiles. I've had a lot of other things happen to my regulator, but never a second stage fall off. Again, IMHO: Either someone (the Tech) did not tighten it or someone (the diver) tinkered with it. Both parties disclaim against that, so we have a case of he said/he said.
4. Diver should have done a dive and checked all connections in a pool or controlled open water environment before diving to 100' with a recently serviced regulator. In subsequent posts (on other thread), I think he realizes that mistake and lesson is learned. Thankfully a lesson learned with little ill-effect.
5. Business 101: The customer is always right (within reason). I believe in this instance, even if the shop is 100% adamant that it was not the tech's fault, you refund the monies and apologize that this happened. Of course for liability reasons, you send a letter, along with the refund, advising of all the other contributing environmental conditions that could have made this happen and disclaim all liability. Advise in the letter that this is an attempt to take care of customer who is dissatisfied for "any" reason and not admission of guilt or liability. Of course, you also state that acceptance of the payment disclaims all further damages and liabiltiy. After all, this is America where 1/3rd of our GDP is legal fees.
If the shop had taken care of this initially, we never would have heard about this at all. As an instructor, I am going to ask the owner of the video if I can use it in class when going through pre-dive checks and equipment. If nothing else, I intend to learn from it. Hopefully the parties involved will do the same.