Is <base href tag necessary?

[s_mack]

Can you guess what would happen in the future if a page was added at "http://example.com/folder/category/my-product-name-456.html"?

When would that come up though? Zen doesn't reference them like that, but rather: "http://example.com/folder/index.php?main_page=product_info&cPath=3&products_id=378"

So... are we talking about SEO friendly hacked url's? Is that when I'd run into trouble?