/* Front end */
show_admin_bar( false );
/* back end */
function disableAdminBar(){
remove_action( 'admin_footer', 'wp_admin_bar_render', 1000 );
function remove_admin_bar_style_backend() {
echo '<style>body.admin-bar #wpcontent, body.admin-bar #adminmenu { padding-top: 0px !important; }</style>';
}
add_filter('admin_head','remove_admin_bar_style_backend');
}
add_action('init', 'disableAdminBar');
Modified version of http://wp.tutsplus.com/tutorials/how-to-disable-the-admin-bar-in-wordpress-3-3/