Hmmm... All interesting. But really, this goes a bit deeper. Here's what I think...
From my experience, the average Open Water diver should be okay with 4-6 dives. I have had divers that are phenomenal, and those who I have failed, purely down to retention of information and comfortability with skills and waterwork. It is a very hard thing to quantify. In an ideal world though where time and money constraints were no object, the more the better, so I would say 10-15 dives at least.
I believe that the standards for Advanced Open Water should be four dives per specialty, depending on the specialty, with a lecture on each and knowledge review. Ice diving? That's a different story, as are some others.
DM/AI's should do a minimum of a three month work off in a dive centre environment, accruing at least 100 dives before they start, and finishing with 200+. That and about four or five random half hour lectures each to teach them how to talk to a class in prep for instructors (start the learning asap), stress management, tank filling, logistics, paperwork, the whole lot - all under the supervision of a good Instructor, that is. This will give them a reasonable breadth of experience for me to consider letting them go running off with green certs.
It's also important for them to assist with introductory divers. This is one of the things that people don't get much experience with these days, and I can say that my life as an Instructor was made far easier by dealing with a couple thousand intros before I started courses. If possible, they should get as many knowledge tests and lectures done too. They need to be able to work the back deck of a boat, plan ahead, and really start automating the "Thinking Diver" idea. All this, and they need to have a good work ethic in hand.
I disagree that number of dives has nothing to do with your ability level - the fact is that every dive is a different set of circumstances, and in every dive there is the possibility of things going wrong. Currents, o-rings going, tanks slipping out of tank straps, fins breaking, (god forbid) out of air scenarios, lost buddy etc etc. The more you dive, the more chance these things will arise, and how you deal with these things are relative not only to you, but to whether you've dealt with them before and then this translates into how to try NOT to see it happen again. It's here that you've really worked out how to be SAFE, and be your own critic.
Now - Instructors. This is the biggest point of contention for me. I've been doing Instructing at various levels about five and a half years now, so I'm hardly old school. But I can see the calibre of instructors slipping and slipping. The problem is that they get certified too early. The instructor prep after DCSI/DM should take at LEAST 6 months. This zero to hero crud doesn't fly with me at all.
You should be assisting, assisting, assisting and trying to get as much exposure to the public and the industry as possible. That's why it's great to do high volume areas such as Egypt and GBR etc, as long as your trainers are good. If not though, then that doesn't mean you're at a disadvantage. It allows you to become incredibly efficient at problem solving and talking to/diving with LOTS of customers. This is where a lot of OWSI's fall down. Anyone can regurgitate key points and values and all that crap in the pool, and you may be great when everything's going right, but dealing with customers at all levels, pressure situations and any pursuant fallout is a real test of your calibre.
So really when you think about it, it should take at least 2-300 dives to get this all right. I agree on the Trainer/Examiner being independent. That's a given. People who certify their own students are their own worst enemy in terms of quality assurance. They need to be put in a pressure situation on the day, and get used to being under the microscope as we all are representing the industry.
Phew. If I missed anything, I'll get back to you
-- Nemo