Overview:

There is an existing live web application which has >40 000 users and organization accounts.
We want to enhance it with social networking/communities functionality.

Target:

We are still writing the specs for this project so not all requirements are 100% clear.
But as a beginning, the plan is to extend each account with its own blog, and its own forum, and a "personal page" with updatable contents.

Specifics:

Drupal web will reside on a separate server, and has to interact (interlink, and exchange data) with the currently running web application (for example each account opened in the existing application should open/close corresponding entries in Drupal one).
We did not have time to research Drupal docs with regards to interfaces it provides for this; but we have full support for the existing app and changes/additions in its code are no problem.

I've heard great references for Drupal as the one of the best and most flexible platforms to achieve this.
We are looking for developer/consultant which can deal with Drupal side - from Drupal installation to eventual customizations of code and modules (if needed). Telecommuting is OK.

Questions are welcome.
Email: vnaskov[at]rogers[dot]com
Thanks everyone.