Here's why I don't think Atlanta can duplicate or really compete with Silicon Valley:
Atlanta just doesn't have as many "crazy" people who are willing to take a risk on "stupid" ideas. I think this article sums things up well (just substitute Georgia for Michigan):
http://www.metromodemedia.com/blogs/posts/TMeloche3037a.aspx
Atlanta will never have enough "crazy" people... while Atlanta is one of the most progressive cities in the South, it's still pretty conservative which doesn't really allow for thinking differently and taking risks on a more massive scale.
It's also good to note that a lot people from either GT or Emory move to either New York or California after graduation or shortly after...