Here is how you can add the category tree path in the product view page.
Edit file app/design/frontend/{interface}/{theme}/template/catalog/product/view.phtml
And in the section that you want the categories to appear add this code:
<?php $categoryIds = $_product->getCategoryIds();?>
<?php foreach ($categoryIds as $categoryId) :?>
<?php $tmpId = $categoryId;?>
<?php $categories = array();?>
<?php while($tmpId != Mage::app()->getStore()->getRootCategoryId()) : ?>
<?php $category = Mage::getModel('catalog/category')->setStoreId(Mage::app()->getStore()->getId())->load($tmpId);?>
<?php $categories[] = $category;?>
<?php $tmpId = $category->getParentId();?>
<?php endwhile;?>
<?php for ($i = count($categories) - 1; $i>=0;$i--) :?>
<a href="<?php echo $categories[$i]->getUrl() ?>"><?php echo $categories[$i]->getName() ?></a>
<?php if ($i >0 ):?>
-><!-- this is the tree separator. change to whatever you like-->
<?php endif;?>
<?php endfor;?>
<br />
<?php //break;//uncomment this if you want only one category tree to appear.?>
<?php endforeach;?>
I hope this helps someone.
Keep in mind that this will make your page load a little slower, but I don't think it's something you should worry about.
Any comments are welcomed.
Marius.