I've just noticed that the long, convoluted Facebook URLs that we're used to now look like this:

http://www.facebook.com/example.profile#!/pages/Some-Other-Page/123456789012345

As far as I can recall, earlier this year it was just a normal URL-fragment-like string (starting with #), without the exclamation mark. But now it's a shebang (#!), which I've previously only seen in shell scripts and Perl scripts.

Does #! now play some special role in URLs, like for a certain Ajax framework or something since Facebook's interface is now largely Ajaxified? Or is it for some other purpose?