Been thinking about this a lot; Dev's wife's experience in her first BJJ class (described on his blog here) plus the comments that followed helped me to coalesce some thoughts on the matter. I'm now going to stick my foot in my mouth and down my throat-- here goes!
BJJ is obviously a physical activity. You can be good, even great, at it without necessarily being good at other, non-physical activities.. like writing, teaching, explaining, or designing curricula. In fact, you can be a great communicator of information and still not be great at designing the curriculum-- the ORDER of the topics that are taught can be as important as HOW they are taught, I would say.
"Those who can, do; those who can't, teach" is a common aphorism that saddens me-- because those who can't do it usually produce students who can't either, but those who can do it often can't teach it effectively.
It's a rare person who can both do well and teach well.
So-- generations of jitsukas are being produced, and have been produced, by a system that works okay, but not great. If only there were more instructors out there like Donald Park, or Cane Prevost (who blogs at The Gentle Art) who focus as much effort on finding the best way to teach, lead, and communicate concepts as they do on discovering and executing the best techniques.
Dev's wife is exactly right. No one really learns to swim well by getting tossed into the deep end of the pool. At best, you splutter, snort, flail wildly, clock someone else upside the head, and eventually learn to dogpaddle to the side. At worst, you feel like you're drowning, hate the experience, and flee the scene never to return. We don't teach kids to swim that way.. we start in the baby pool getting comfortable with water on our face. We build up to actual swimming gradually by teaching them the subsidiary skills they need and by bolstering their confidence.
More data points which, to me, seem to point in the direction of a mandatory noobs-only BJJ class which has to be "passed" before the student is allowed into "adult swim."