How bad is it to use Node_load in a loop in drupal 7?
You should never need to use node_load() in a loop, that's what node_load_multiple() is for:

$nids = array(1, 2, 3, 4, 5);
foreach (node_load_multiple($nids) as $node) {
  ...
}


It's hard to imagine a scenario where loading the nodes individually would be necessary or desirable.