/**
* Disable admin bar on the frontend of your website
* for subscribers.
* Add this to <them>/functions.php
*/
function functionsphp_disable_admin_bar() {
	if( ! current_user_can('edit_posts') )
		add_filter('show_admin_bar', '__return_false');
}
add_action( 'after_setup_theme', 'functionsphp_disable_admin_bar' );