Is what you humans call - devops?
I'm interested in this area as I've developed a framework for carrying out continuous integration. It is currently primarily for Drupal and is currently going through a code cleanup - but it does work and I've used it at a couple of companies - it is at: https://github.com/SSVC/pullpush/wiki . Version 1.0 should be available in the next few weeks.
To me - the key points are:
* If it is small changes then tweaking the live site should be do-able - but what about large upgrades?
* Rather than pushing changes up to a live site we should pull live data down to a new version of the site.
* How easy/quick is it to roll back to a safe, known good version if a rollout goes bad.
I've also posted a blog post about another way of getting continuous integration for Drupal sites - http://www.freewayprojects.com/2013/08/maybe-we-should-use-separate-drupal-sites-for-backend-data-and-for-front-end-presentation/
As websites contain more and more data this subject is becoming more and more important.