[jdietrich]

A teaching ladder is a linear system, not a pyramid. I get a lesson, I give a lesson, one for one. Reciprocity is used purely to prevent the free rider problem. Participants freely barter their expertise rather than paying for lessons. This is a perfectly stable arrangement - the ladder in the first link has been running continuously since 1994.

The person at the top of the ladder is essentially performing a public service, because they don't get the benefit of learning from a more experienced player. If they leave then the ladder doesn't collapse, the second strongest player simply becomes the leader.

Ladders are commonly used as a competition format in many sports. They provide an excellent way of giving players a challenging but enjoyable game. Teaching ladders are simply an elaboration on this format.