To get and idea of this ill-minded (or not) project :
and about how to do it :
The first thing we need, is really skilled (obviously not like me) Drupal people to help build a decent site and more important to set up the encryption of the Private Messages in Mysql database. Then will come database replication and so on ...
If there is any freak out there interested enough, contact me at email@example.com and let's start working !