I'm sure I'll get crucified for it, but it occurs to me that there's a sliding scale of real risk when it comes to certain "specialty" certs.
Not specialty certs, all certs. My other half didn't do an AOW course for a long time - with 15 years of diving in cold water, her OW card never restricted the diving we wanted to do. She only every did her AOW course because she lost her OW card and it was just as easy to do the course as it was to get a replacement card.
There is a risk that a "wreck certified diver" will still so stupid things, like go through a restriction that is too narrow for two divers to pass through, or wander out of the light zone with no guideline etc etc. There's also a risk that someone who is an OW with 1000 dives will do this. How do you compare the risk? How do you quantify it? How do you make objective decisions?
Proof of certification is one tool in the box. It certainly provides an objective "standard" - then you make decisions on the exceptions you want to make, as opposed to having to make a decision on each and every diver.
Most specialty certs are a joke. I feel like nitrox isn't one of them due to the added variables it introduces in your dive plans. Experience should be enough for depth/wrecks/night diving but I'm not sure a log book is the best way to prove that experience unless you have logs signed off by instructors or stamped by a shop as you can easily fabricate dives by just writing them in and scribbling someone else's name to "verify"
I tend to disagree. A specialty course is only a joke when there's a combination of an instructor who doesn't care and a student who doesn't care.
If the student really cares, they'll take the time to hunt around and find the right instructor for them and will get a lot of value out of any course.
If the instructor really cares, they'll do their damndest to add value where they can in the interests of the student.
I also disagree that "experience alone" is enough to prepare someone for wreck diving. 1000 wreck dives does not make someone competent at wreck penetration. I guess you might be able to self-learn how to use a guideline, and you might be able to recognise which passageways you couldn't share air through, feasibly you might even start to get an awareness of line traps and how to avoid them.... but probably only after a few foul ups and close shaves.
You can learn these things from other experienced wreck divers much more quickly and safely than trying to learn them yourself, I agree. One way of doing that is through a good wreck course. Even though it's not "officially" in the syllabus, we teach about line traps on our basic wreck course. We simulate air sharing through a restriction (dry run). We demonstrate the advantages of long hoses. We hammer home the importance of good fin technique. We talk about team protocols for penetration. The list goes on..... and I haven't even started on our advanced wreck course that we offer.
It's not just us, there are plenty of really good instructors out there who teach this stuff (or the equivalent for night, deep, or whatever). But you have to hunt around and ask the questions, talk to previous students and basically take control of your own learning.
Cheers AndyNZ 
