We've already accepted that hybrid cloud is the future of infrastructure for most enterprises - research repeatedly confirms that cloud is and will be a major component of enterprise infrastructures. In other words, enterprises expect their hybrid cloud architecture to consist not of a self-contained pilot project in the public cloud but a full-blown, integrated application farm stretching across multiple datacentres in multiple geographies, probably across multiple service providers.
Private cloud to the fore?
Yet there remain those who argue that a private cloud has a leading role to play in the armoury of enterprise's infrastructure. The issues over moving to public cloud are likely to be the same as they were at the start of the cloud revolution: enhanced control over costs, data and the infrastructure.
There are arguments a-plenty as to why public cloud can override many if not most of those objections, but one trumps them all. The fact remains that building and maintaining a private cloud is now near-impossible for all but the very largest of organisations, so high have the barriers to entry become. In effect, such an enterprise would be putting itself in competition with the very largest cloud providers, who have a number of significant advantages tilting the balance in their favour.
They key advantage of the cloud providers is what RedMonk analyst Steven O'Grady described as relentless economies of scale. To paraphrase the core of that long and interesting analysis, O'Grady points out that large cloud providers build their own servers and other hardware, they can purchase components at huge discounts, and their fixed costs are amortised over a very large number of customers. This drives down unit costs and increases efficiencies - and to cap it all, the technical challenges make such a provider a very attractive place to work; for the enterprise, finding talent is often one of the toughest tasks.
The upshot is that the mega-scale cloud vendors can offer services at prices way below what it would cost any enterprise to replicate - even on a small scale, because small doesn't cut it when it comes to cloud provision. A major cloud provider's datacentre - one of many - may contain typically around 50,000 hosts on 1,000 racks. This gives cloud providers enormous economies of scale, given the high fixed overhead of running a datacentre, and driving this metric forwards is a key competitive advantage for them.
Could a private enterprise datacentre achieve anything like those levels of scale? Seems unlikely, as costs will loom large in any corporate discussion about an enterprise infrastructure refresh versus going to the cloud. What remains an advantage for the enterprise private cloud is control, and maybe security. But is the enterprise willing to cough up the cost of that comfort blanket?
Gartner analyst Tom Bittman gives the answer when he shows that application workloads are growing much faster in the cloud than anywhere else: in 2011 about three percent of all VMs were running in public clouds but by 2015 that number was 20 percent. Enterprises have voted with their wallets.
 RedMonk - The Scale Imperative. http://redmonk.com/sogrady/2014/12/01/the-scale-i...
 Thomas Bittman, Gartner: Some Perspective on the Explosion of VMs in the Cloud. http://blogs.gartner.com/thomas_bittman/2015/03/0...