What do Twitter and Gawker think of hash-bangs URLs?
My answer to What do Twitter and Gawker think of hash-bangs URLs? on Quora
As of December 2013 (and potentially much earlier, I don’t have the exact dates) both Twitter and a Gawker have moved away from hash bang URLs, so my guess is they turned out not to be a good idea.
Most browsers now support the HTML5 history API which allows the usage of proper URLs while still fetching new content using Ajax without triggering a full page request.