Just to take an alternative view, I'd like to suggest that there is a real human need for mass bonding, something that large seminars can satisfy, and small classes can't. ... I think there is another aspect to teaching: how we get and keep the students' minds most completely engaged.
I understand this reasoning, however, unless you're engaging in martial arts as a business, the student is responsible for keeping their own mind engaged in their practice.
I do think there's a certain responsability for a teacher that sees themself as an educator to present the subject matter in a way that does't put people to sleep, but it's still the student's responsibility to give the interest and attention necessary to stay connected.
Large taikai or seminars are good for taing part in history and making new connections with people from far away or getting "jazzed" and charged up, but the chances for learning are much better in small groups.