Re: In the dojo, 90% of Aikido is uke
All the ways of incorrectly being uke should be highlighted to students from the begining of their training in aikido.
The first 4 examples given are easy to deal with, the errant uke can be shown the 'right' way to move as opposed to the 'wrong' way.
The last example given the 'teacher uke' is a much more complex beast. If someone is doing 'bad teacher uke' then this needs to be discouraged by the dojo sensei ( unless it's the sensei themselves doing it, then there is no easy answer ).As has been pointed out, this creates frustration and inhibits learning.
There is however 'good teacher uke' which requires good ukemi skills, and sensitivity to the level of the nage.
If I am teaching and I can't see an obvious problem with a students technique, I will make ukemi and the problem will become apparent because my following will reveal the issue that needs to be looked at.
Of course I could disregard the students grade and make it impossible to throw me, but no one would benefit.
The use of ukemi as teacher in aikido is imperative, the teaching of good ukemi skills are fundamental.
Personally it was when I started to focus on the 'art' of uke rather than learning to master techniques that aikido started to reveal itself to me.
just a few thoughts.