I think that SEO is really making things worse for URLs. Remember 4 years ago, when "The URL was the New Command Line"? And it was considered a feature that you could look at a URL like http://site.com/user/3916 and hack it to get similar pages for other users? Can't do that with http://yoursite.com/this_was_an_article_that_i_wrote.
Seems like a step backwards.
I built these a while back but they haven't seemed to pick up traction. str8.to uses google's "i'm feeling lucky" - vanity urls without having to go register them.