This article is rightfully making the rounds, it’s really important that you read it. For those not familiar with hash-bangs, it’s the newfangled “solution” (from Google) to create AJAX-crawlable websites. The best real-life example you’ve likely seen is the URL structure of New (is it still considered “New”?) Twitter, e.g. http://twitter.com/#!/jchristopher
#! doohicky is a hash-bang, and it’s causing a ruckus, recently very much so for Gawker and it’s recent massive redesign. Definitely give the article a read, it’s worth it.