That's not actually clear to me. There are some posters who say the same thing over and over, but you only get to count that once. I am more impressed by what I see on dive boats and at resorts around the world; not perfection, but pretty good, in general. There are the truly terrrible, of course, but they are in the definite minority.
You should note that only maybe 1.5% of people EVER leave a review, and that people are far more likely to leave a negative review than a positive review.
If I read ScubaBoard I can run into 15-20 people saying the same thing over and over and over and over, with no facts to back them up. Sorry, that doesn't cut it for evidence. I can find more people telling me the earth is flat.
I could see that the Scubaboard population might not be representative, and that there is a lot of hearsay and unfounded agency bashing, but to claim that there is no problem at all, and implying that the people complaining about issues they have had are lying (re: "with no facts"), seems like a far cry from reality in my experience.
I have done exactly one guided dive in a group with a PADI dive center in the Mediterranean, and it was worse than I expected. It matches most of the stories I've read here on Scubaboard, so even if the sample size is very small, it's an indication to me that these stories are not made up, and that they're probably not that uncommon. They might be a minority of divers, like Tursiops suggest, but if 30-40% (or even 10-20%) of divers are train wrecks I would say there is a big problem with the dive industry.
What I experienced was certified divers with no buoyancy control, buddy skills, or autonomy in the water. Half of the divers in the group were plummeting to the bottom, destroying the bottom, and then rocketing to the surface, like a yo-yo for most of the dive. There were no buddy checks, or even independent checks of their gear. I asked my buddy if they had tested the octo, and they said "Why would I, it's not for me" You can try it if you want". And I was surprised to hear that the worst divers were happy about the dive after the fact. No clue that what they were doing was not ok.
Obviously this is just one example, and I don't have anything specifically against PADI or PADI divers - I received good instruction from a GUE trained PADI instructor, and will gladly dive with any diver from any organization, as long as they don't look like they're going to kill someone underwater. I do believe the stories I read from other SB members, however, and I do believe there is a problem with Scuba training.