I have created and successfully installed a plugin in Joomla 2.5 with the following code

```
<?php
// no direct access
defined( '_JEXEC' ) or die( 'Restricted access' );

class plgCustomFunctions extends JPlugin 
{
    public function onContentPrepare($context, &$article, &$params, $page = 0)
    {
        $article->title = "Something!";
        return true;
    }
}?> 

```

My understanding is that this should overwrite the title of every article. That isn't happening. What am I missing?