Drupal Scalability

Lately I have been approached by many companies questioning the performance and scalability of Drupal.  As more and more sites are using Drupal with many more vistitors, this is a really important issue that needs to be addressed.  I have always considered this issue to be the responsibility of the system administrators but what I am finding out is that most SA's don't know a thing about Drupal or really care to learn.  An vice versa, Drupal developers like myself don't really have an interest or knowledge in working with server optimization.