Since I last blogged about the Copy Short URL add-on, I stumbled across another, very popular example of automatically exposed short URLs:
Wordpress.com as well as self-hosted Wordpress instances have automatic short URLs now, starting with Wordpress version 3.0.
For example, this blog post on wordpress.com about a possible proof for P != NP has the shiny short URL http://wp.me/pr9Ir-1lN.
A recent blog post on my blog, in turn, has: http://fredericiana.com/?p=2921.
Of course, it's a little sad that the auto-generated short URLs on self-hosted Wordpress instances are so ugly, and they are not really short enough to use them easily on twitter or with other character-sensitive applications. But considering how long your average blog post URL is in the first place, it seems like a great win nonetheless.
An unrelated side note: I filed a bug to expose bugzil.la URLs on Mozilla's bugzilla instance. It's not picked up or resolved yet, so if you want to see the support as much as I, feel free to comment on or CC yourself on the bug!