How does Drupal sync data across multiple datacenters and other questions?

I have a few questions on Drupal. i am evaluating it for my company and I keep getting stuck on 3 things.

1. How does drupal replicate content across multiple datacenters? If I have my authoring server in one location, how does the content and metadata stay in sync?

2. I need to use a single sign on solution. How would this work if none of the webservers are shared?

3. If I have content that is the same, can I share it between sites?

Thanks for your time.

Chris