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.
Nick Denton: "Dip in uniques largely because of drop in Google refers. Pageviews (which are driven more by core audience) less affected." -- http://twitter.com/nicknotned/status/61152134929981440
Nick Denton: "Google does not fully support "hashbang" URLs. So we're eliminating them rather than waiting for Mountain View." -- http://twitter.com/nicknotned/status/61465859079671808
Nick Denton: "Yeah, I'd advise against hashbang urls. Will kill search traffic -- even if you abide by Google protocol." -- http://twitter.com/nicknotned/status/62595141927583745
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.