Any password protected info sharing tool....

Question

I'm looking for a password-protected information sharing tool that has the following constraints:

1. Two or more users can upload their ideas and discuss on that idea (like a blog)
2. The discussed things will be shown in a tree kind of structure
3. Should be password protected.
4. Ideally open source and web-based

Answer 1

Yammer.

Answer 2

You could use google docs too :) , now you can even doodle on drawing while you teammates talk endlessly. On a more serious note You can house you own solution using etherpad , an opensource collaborative real time editor