Is it a private cloud service, or a public cloud service? It’s not quite so binary. I first explored this in my post Virtual Cloud Privacy is Gray a few months ago. There are two relative dimensions that determine how “private” or how “public” a cloud service really is:
Service Control/Ownership: There are two ends of a spectrum here – complete implementation ownership, and complete lack of ownership and control of implementation. But there will be many examples in between of partial control, shared ownership, etc.
Service Access: Also two ends to this spectrum – at one end, usage is extremely exclusive, while at the other end, anyone who chooses can access the service. Again, there will be many examples in between of limited access, industry-only access, controlled partner access, etc.
These two dimensions are coupled at the extremes, but there are many variations in between. Each has different security/privacy, cost, customization and elasticity attributes.
Many of the cloud services that emerge in the next few years will fall somewhere in the middle (consider the customers choosing Exchange Online Dedicated, or paying for Reserved Instances from Amazon). Understanding the trade-offs and options is critical. This is an important area of research for me right now (two research notes completed, three more in progress!).