+1 for everything Aneesh said, but I also wanted to add that the public cloud offers opportunities in data sharing that academia hasn't yet provided, specifically the ability for collaborators to bring their code to the data. I posted a quote from Jed Sundwall, Global Open Data Lead at AWS in another thread. I think he really nails it when he says that the cloud "completely changes the dynamic for sharing data."

There certainly have been efforts in academia to provide shared computing resources. Cyverse (https://www.cyverse.org/about) comes to mind. At Wisconsin many researchers shared clusters using Condor. But, none to my knowledge come close to the scale, reliability and features of AWS and the other major cloud providers.