This plugin removes the admin bar completely from the public and admin areas of the website. Can be used either as a normal or MU plugin.
Upload this plugin to the
/wp-content/plugins/ directory and unzip it, or simply upload the zip file within your wordpress installation from 2.7 onwards.
Activate the plugin through the 'Plugins' menu in WordPress
Alternatively, move the remove_bp_adminbar.php file into your
/wp-content/mu-plugins/ directory for it to work sitewide automatically.