Google published a specification [1] for "Making AJAX Applications Crawlable" which uses #!. This has been widely adopted; it's plausible that the majority of web apps that store their state in fragment identifiers use this convention. That is why people are using the term "hashbang" to refer to the practice in general.
Once of the reasons Gawker moved away from hashbangs is that they weren't well supported by Google, despite this being a "Google specification". Nick Denton, the founder of Gawker, has some interesting tweets about the use of hashbangs over the past few months:
So here's a high-profile failure of hashbangs when it comes to being indexed by Google. Which means if it's search indexability you want, hashbangs isn't it. The Google spec just isn't mature enough, or well supported by Google search itself.
http://code.google.com/web/ajaxcrawling/docs/specification.h...