de-install

If modules had a function that returned what tables and columns they use, an uninstall module (or a simple function inside system.module) could simple drop them if they are unique to the module being uninstalled and delete the .module file.

A simple hook like:

<code>function rating_db_info() {
  $db_info = array();
  $db_info["rating"] = Array(); // table name
  $db_info["rating"]["nid"] = 1; // Collum name
  $db_info["user"] = Array();
  $db_info["user"]["rating"] = Array();
  return $db_info;
}

function user_db_info() {
  $db_info["user"] = Array();
  $db_info["user"]["uid"] = 1;
  return $db_info;
}

function uninstall_module($module_name) {
  $drop = Array();
  $keep = Array();
  foreach(module_list() as $name) {
    $db_info = module_invoke($module, "db_info");
    foreach ($db_info as $table => $column) {
      // Logic to add tables to drop here. No time to think about it now 
    }
  }

  foreach ($drop as $table => $column) {
    // $sql_query to drop
  }
  unlink($module_name);
}

Just a thought