magento/magento2 — pull request #126 by srenon (2012-11-10 17:27:31+00:00)
Title: Update app/code/core/Mage/Tag/Model/Resource/Tag/Relation.php

When deleting a product that is assign to a tag by unchecking the checkbox under "Products Tagged by Administrators" (Catalog -> Tags -> All Tags) it will also delete all tags associated with that product.

see http://www.magentocommerce.com/bug-tracking/issue?issue=14255