Howdy, I have created a YQL API module implementation along with yql_autotagging plugin module at http://drupal.org/project/yql
In addition there is a sub-module yql_autotagging that is a plugin for autotagging using the YQL API module. I'm using it on a site successfully so far, although it could use more testing and robustness.

I ask that you give it a try, and if it works for you please link to it here. Let me know if there is anything further I can do to collaborate with you. Cheers.