I'm reminded of an interview with Threadgill Sensei that I read a couple of months ago. (http://www.aikidojournal.com/article...light=Takamura
) He explained (paraphrasing) that even in a koryu, it is impossible for any teacher to pass down everything he knows. No matter how excellent the teacher or how diligent the student, one lifetime is never enough.
It is therefore one of the duties of each headmaster to add the results of his own studies back into the tradition. Every generation loses some things, but rediscovers others, and that's how the art survives.
The claim that all of Ueshiba Sensei's aikido was passed down (to anyone), and therefore our modern training as defined by his students (however capable) cannot be questioned is fundamentally bad for the long term health of our art.
I really enjoyed this point! Even if O Sensei only taught in one location with one group of people, chances are good there would have been different kinds of uptake/transmission; different emphases would manifest.
Also, I wonder how much of the numbers issues simply has to do with loose language styles. I mean, the appeal to round numbers has been used for one thousand years. Now, pardon me while I go get my 40 winks.