Amazon got an early start in public cloud IaaS and that's one big reason why it's dominating the market. But this year, some big name players entered the cloud IaaS space hell-bent on taking some of the steam out of Amazon's sails.
Microsoft launched IaaS on Windows Azure and immediately vowed to match Amazon's frequent price cuts. Google unveiled Google Compute Engine and introduced per-minute billing in a bid to improve upon the per-hour pricing that Amazon uses. VMware, whose server virtualization software has long been the stuff on which private clouds have been built, launched vCloud Hybrid Service.
Microsoft and VMware are pitching the value of having a compatible infrastructure from a single vendor for both public and private clouds. Google's enterprise story isn't clear yet, but given the roster of tech talent it's got in-house building all sorts of insanely scaling services, its cloud IaaS will certainly be a force to be reckoned with.