Landmark forum did indeed used to be EST. The guy who started it, used to be a mucky muck in scientology. I've known a lot of people involved in Landmark, and I have a deep suspicion of their methods and their principals. Some of the more destructive narcissists I've run across had their behavior seemingly sanctified by Landmark.
One voice teacher at my college was disciplined for coercing her students to participate. I had an acting coach who was a Landmark follower, and he tried to use their methods in his workshops - no breaks for the bathroom, eating. He also used his position to try and gain sexual favors from the participants, and to behave inappropriatly towards underage females in the class. His philosophy seemd to be,"If I want it, I should have it", with no regard for his impact on others. I've seen it have the effect of replacing insecurity and fear with grandiosity and insensitivity.
I would be very, very leery of becoming involved with Landmark. They don't use as drastic methods of brainwashing as they used to, but it's still very much coercive. The long hours, infrequent breaks and social pressure serve to break down a person's natural boundaries and sense of reality, making them very vulnerable to suggestion and pressure. They also basically require that participants bring more people in to "witness" their transformation, and then encourage them to take longer and pricier classes. I've been pressured by several people to join up, and they get very grumpy when I say I'd rather give my money to a licensed therapist.