Dominance theory, pack theory, and the forms of training Cesar uses are all another way of saying AVERSIVE training. It is a very traditional technique that is starting to lose hold in the training world for many reasons. 1) It's dangerous to try at home without a trainer 2) Dogs can aggress back 3) Dogs will find other outlets for their aggression 4) Dogs will find other people to dominate if the REAL problem isn't solved 5) It causes a loss of trust in the relationship 6) It stresses the dog, and can cause real damage and pain (I've seen this occur) 7) It doesn't work on all dogs (even though Millan's series shows the dogs it does work on - READ THE NOTE the author Shibashake makes herself after she weighs the pros and cons in the article below, 'Aversive Training Pros and Cons').
Keep in mind that many many trainers train the Cesar Millan way to this day with all types of animals - horses, monkeys, show/agility dogs, anything with a leash or lead. I have personally been taught by trainers of this mindset as well. I have as a student and trainer taken an OATH that I will not train aversively if it is avoidable. But if it seems that this is the only option I must make every effort I can to solve a problem.
I have included some articles from the NYT on Cesar Millan, and one from a page detailing some pros and cons of this form of training. Weigh it out yourself, everyone!
ARTICLE: Pack of Lies (August 2006)
ARTICLE: Families Borrowing from Cesar Millan (Nov. 2009)
ARTICLE: Aversive Training Pros and Cons (2009)