Wikipedia uses something similar to what I described under the covers. There's a unique id assigned to a page, but it's ALSO accessible by a title. Internally, the page id is used to refer the page from other items, not the title[1]. This is sort of equivalent to having one or more names associated with your SSN, if you are in the US. Which makes sense, because names are not unique.

1: http://goo.gl/T7DfoC

Edit: HN garbled the wikimedia URL, so I used a shortener.