I know this would never happen, but wouldn't it be awesome if agencies made it mandatory for instructors to list the days they were training and where they were training at. Imagine:
Peter 4/2/2015 Teaching 4 Cavern Students at Ginnie Ballroom
Then, if there were rumors about bad habits about a particular instructor, other instructors or people could go and witness what's happening. We'd know where and when to be there. There'd be multiple accounts of what happened good or bad.
Another benefit would be that two instructors from two different classes wouldn't plan on being in the same passage at the same exact time trying to do the same exact skills. Ever try to navigate through the catacombs. You get all setup for that dive, and when you get there, you realize there's already another team in there, completely screwing up your dive plan?
Of course, I realize there's a certain hint of nazi'ism to this approach. I'm not sure it would ever work, or should work. Just throwing some ideas around.