Google's Picasa Web Albums show a user friendly string in the album URL. I think this might be new, but I can't see any notification of the change. I thought Google used to show some occult identifier, but maybe that's because I'm used to private albums that are not shared.
Google encourages links to albums and photos that embed that URL.
The URL is formed by the name of the album.
You can edit album names.
When you edit them, you change the URL.
The links then break.
Google did the same thing with Blogger for years, a few months ago they changed the behavior so the URL no longer changes even when one edits a blog title. That was a bad mistake that took Google far too long to correct, but one could come up with some perverse rationalization for the original blunder.
I can't rationalize this one at all. Google needs help.