There ARE rules, such as only one person per activity (most activities).
Montessori teach letters, spelling, reading and phoenics from 3 years of age!
These are the two biggest gripes I have with Montessori and why I wouldn't send my child to one. I don't like the "one child to an activity" thing- where are the social skills in that? And I also don't like the empathsis on phoenics, tracing letters etc from such a young age. I don't think the research has found those to be these best ways for children to learn to read and write.

Personally Montessori is way too structured. I love the idea of respect and like all early childhood philosphies I'm sure it has many good points.