t() called in a global scope

As described in these issues http://drupal.org/node/147322, http://drupal.org/node/338443, t() being called in a global scope when $locale is not set can cause performance problems.

Maybe it would be a good idea to have a coder rule/test that would check for that? I'm not sure the best way to check for that, but would be glad to make a patch with a little advice in the right direction.