Matthew Turland has ammended a previous technique he suggested about using a centralized set of plugin loaders for Zend_Form elements (part of the Zend Framework) because of an issue it can cause with the Zend_Loader_Plugin.

The bug entails Zend_Loader_PluginLoader allowing multiple instances of the same path to be added per prefix. This becomes an issue because of how Zend_Form handles adding subforms. [...] If both the form and subform are using the same plugin loaders, the bug causes the same paths to be added multiple times.

As of the posting of this article, the issue has not been corrected. The solution is outlined in the description of the bug if you want to correct the problem yourself until the full patch is included.