add_action('bp_ajax_querystring','bimber_custom_exclude_users',20,2);
function bimber_custom_exclude_users($qs=false,$object=false){
    //list of users to exclude

    $excluded_user='1,2,3';//comma separated ids of users whom you want to exclude

    if($object!='members')//hide for members only
        return $qs;

    $args=wp_parse_args($qs);

    //check if we are searching for friends list etc?, do not exclude in this case
    if(!empty($args['user_id'])||!empty($args['search_terms']))
        return $qs;

    if(!empty($args['exclude']))
        $args['exclude']=$args['exclude'].','.$excluded_user;
    else
        $args['exclude']=$excluded_user;

    $qs=build_query($args);


   return $qs;

}