With 2010 and the beginning of a new decade a new era of computing technology and architecture, commonly referred to as 'cloud computing', emerged following the revolution of virtualisation in the datacenter and on the desktop during the latter half of the previous decade.

The information technology industry was set alight with visions, research, tools, roadmaps and services to tempt would-be cloud-adopters to take the plunge and reap the benefits.

So what benefits exactly are we talking about?

From an infrastructure perspective the benefits are clear: elasticity, scalability, continuity and automation as championed by early movers such as Amazon with their Elastic Compute and S3 services. Amazon's initiative has provided the industry already with a common API for many cloud computing infrastructure operations. Amazon continues to add value to their core offerings through the addition of hosted DNS and their Elastic Beanstalk service - as such Amazon is a leader of public cloud computing services.

Meanwhile, VMware - a global leader in virtualisation was helping the 'enterprise' user deploy equivalent capabilities internally - their technologies have had a dramatic effect with heavy computing users who are able to tear-up and down infrastructure on-demand, re-locate servers (virtual) across physically separate datacenters effortlessly and ensure exceptional business continutiy for these organisations with an elastic infrastructure founded on virtualisation technologies.  Vmware is a leader in private cloud computing technologies.

Building on these concepts infrastructure service providers margins faced a significant challenge and they were prompted to look beyond their traditional hosting services and the emergence of "Platform-as-a-Service" computing began to take hold.  Early movers such as Opsource provided a coherent set of services on top of physical infrastructure to enable organisations to deploy enterprise-grade software services without the hassle of infrastructure management and service  component integrations such as identity, security, monitoring, accounting and billing.

Salesforce.com is commonly referred to as the poster-child of "Software as a Service". Their success is irrefutable and this has spawned a diverse marketplace for complementary 3rd party solutions i.e. marketplace, an API to integrate with their technologies and client data, all delivered "-as-a-Service", the end-user's previous 'headache' of infrastructure and platform selection, design, management and maintenance has been removed - barriers to integration have also been significantly lowered thanks to the Force API and marketplace.

Cloud computing's roots go back to the days of dumb terminals, time-based computing and mainframes.  Today, cloud computing can be seen as three distinct layers: Infrastructure as a Service, Platform as a Service and Software as a Service.

However, the issue with this is that -as-a-Service can actually bring new and different constraints so while the 'revolution' is solving one set of problems it is accompanied by another set of new, if not familiar, problems. Can multi-tenant architecture satisfy corporate legal requirements? Investing your data in a solution such as Salesforce brings the constraints of being tied to the strategic and tactical plans of Salesforce - you are beholden to their roadmap and corporate agenda, if you are unfortunate enough to suffer a bug that no one else has what are the chances you will be able to get this resolved expediently? How portable is your investment - can you move your data to another solution provider? If your business model changes can your service provider meet these challenges?  Amazon began their operations in the USA, they now have datacenters in several other geographic territories though they are not globally ubiquitous and are governed by US law and exposed to the issues of client safe-harbour, secure and confidential data. Initiatives such as ITIL and CoBIT championed the idea of corporate Service Level Agreements with their internal IT service providers, how can a single tenant negotiate the appropriate SLA amongst thousands of other tenants, let alone enforce it? Google's applications are fantastic yet access is not ubiquitous - some countries block the use of Google's services. Fundamentally, who has sovereignty? The client is much less empowered than when they ran their services using their own infrastructure and one of the reasons private cloud architecture is booming.

The solution is not a simple one, these new services are exceedingly compelling, bringing with them increased utility, productivity and performance for end-users though as inferred, not without challenges.