Why are people put off from posting here?

The discussions here at ChinesePod are dominated by a handful of people.

I ask myself: Why is this so? ChinesePod seems to have more customers and even much more non-customers (like me), and, last but not least: Chinese becomes more and more important.

Any ideas, how that can be changed?

I would like to see more different people discussing Chinese here, not only the same group of 10-20 persons (see here).

Sometimes threads are even changed in topic from this inner circle (like this one) - ok, you cannot prohibit this, but this may put people off ...