Plugin developers: The new wp_add_script_before() function has been removed from WordPress 3.3. (In r19573.)

In an IRC discussion it was discovered that it was not architected in an ideal way, and some inconsistencies were discovered relating to how scripts are loaded. For more see the end of #11520.

If you want to echo data to be used in your script, you can continue to use wp_localize_script() as before. Since it now uses json_encode(), it is a bit more flexible (can do nested arrays, for example). In 3.4 we hope to introduce a few more enhancements in this area.

(For those just tuning in, please note that wp_add_script_before() was originally new to 3.3, so this will not affect existing plugins.)