Although the cloud still has its skeptics, some new research from International Data Corporation (IDC) suggests their influence is going to dwindle — and fast.

Global spending on public cloud IT services is expected to exceed $40 billion by the end of this year, IDC reports. By 2016, cloud spending will approach $100 billion.

Over this four-year period, that represents a 26.4% compound annual growth rate. That’s five times as fast as the IT industry overall, according to IDC.

Which cloud services are going to be the hottest markets? IDC says Software as a Service (SaaS) will “claim the largest share” of cloud services spending over the next five years. Interestingly, however, cloud storage and Platform as a Service (PaaS) will grow faster.

This probably comes as no surprise to cloud providers. Infrastructure as a Service (IaaS) is on track to become commoditized (if it hasn’t already), and cloud providers are recognizing that selling SaaS and PaaS will be more profitable over the long term.

From a geographic perspective, the United States will occupy the largest share of the cloud market, IDC reported. Following closely behind the U.S. are Western Europe and the Asia-Pacific region (minus Japan). But the fastest-growth area for cloud spending? Emerging markets, whose “collective share [will] nearly double by 2016 when it will account for almost 30% of net-new public IT cloud services spending growth,” according to IDC.

Social gaming giant Zynga — best known for flooding your Facebook notifications with requests to harvest Aunt Susan’s Christmas-themed strawberries — may soon become the competition.

Although it doesn’t cite any sources inside the company or elsewhere, CloudTimes reports that Zynga is “on its way to becoming a serious competitor to Amazon’s robust Infrastructure as a Service, since the social network gaming giant will soon sell cloud IaaS to game makers in need of a hosting platform.”

If Zynga’s IaaS aspirations are true, then it was only a matter of time, wasn’t it? Zynga began pursuing a hybrid-cloud strategy last year when it launched its private cloud, zCloud. Why not capitalize off of any its excess capacity by renting out computing resources to other gaming companies? After all, that was how Amazon Web Services got its start. And given its acute focus on optimizing a platform for the rigors of online gaming, Zynga will be in an interesting position to tap into the online-gaming ecosystem.

No other media outlet has reported on this story, and we’re awaiting a response from Zynga’s press team to confirm the news. We’ll post any updates as we get them.