Setting the site name of a Drupal site

I just spent a frustrating couple of hours beating my head against a Drupal site, trying to change the site name (that appears in the site banner and title). No matter what I set in the admin/settings page, the site name remained unchanged. The database was being updated correctly:

mysql> select * from variable where name = 'site_name'\G
*************************** 1. row ***************************
 name: site_name
value: s:20:"My Fancy Drupal Site";

but the old name was still displaying on the site (and every time I went back in to admin/settings, the name had reverted).

Finally, I remembered this section of settings.php:

 * Variable overrides:
 * To override specific entries in the 'variable' table for this site,
 * set them here. You usually don't need to use this feature. This is
 * useful in a configuration file for a vhost or directory, rather than
 * the default settings.php. Any configuration setting from the 'variable'
 * table can be given a new value.
$conf = array(
  'site_name' => 'My Drupal Site',
//  'theme_default' => 'bluemarine',
  'anonymous' => 'Visitor'


So I commented out that 'site_name' line, and everything worked as expected.