Cloud BI The reality (From Warne's blog)

Three Types of Cloud Services with BI Examples

Software-as-a-Service (SaaS). SaaS delivers packaged applications tailored to specific workflows and users. SaaS was first popularized by Salesforce.com, which was founded in 1996 to deliver online sales applications to small- and medium-sized businesses. Salesforce.com now has 92,000 customers of all sizes and has spawned a multitude of imitators. A big benefit of SaaS is that it obviates the need for customers to maintain and upgrade application code and infrastructure. Many SaaS customers are astonished to see new software features automatically appear in their application without notice or additional expense.
Within the BI market, many startups and established BI players offer SaaS BI services that deliver ready-made reports and dashboards for specific commercial applications, such as Salesforce, NetSuite, Microsoft Dynamics, and others. SaaS BI vendors include Birst, PivotLink, GoodData, Indicee, Rosslyn Analytics, and SAP, among others.
Platform-as-a-Service (PaaS). PaaS enables developers to build applications online. PaaS services provide development environments, such as programming languages and databases, so developers can create and deliver applications without having to purchase and install hardware. In the BI market, the SaaS BI vendors (above) for the most part double as PaaS BI vendors.
In a PaaS environment, a developer must first build a data mart, which is often tedious and highly customized work since it involves integrating data from multiple sources, cleaning and standardizing the data, and finally modeling and transforming the data. Although SaaS BI applications deploy quickly, PaaS BI applications are not. Basically, SaaS BI are packaged applications while PaaS BI are custom applications. In the world of BI, most applications are custom. This is the primary reason why growth of Cloud BI in general is slower than anticipated.
SaaS BI are packaged applications and PaaS BI are custom applications. In the world of BI, most applications are custom.
Infrastructure-as-a-Service (IaaS). IaaS provides online computing resources (servers, storage, and networking) which customers use to augment or replace their existing compute resources. In 2006, Amazon popularized IaaS when it began renting space in its own data center using virtualization services to outside parties. Some BI vendors are beginning to offer software infrastructure within public cloud or hosted environments. For example, analytic databases Vertica and Teradata are now available as public services within Amazon EC2, while Kognitio offers a private hosted service. ETL vendors Informatica and SnapLogic also offer services in the cloud.
Key Characteristics of the Cloud
Virtualization is the foundation of cloud computing. You can’t do cloud computing without virtualization; but virtualization by itself doesn’t constitute cloud computing.
Virtualization abstracts or virtualizes the underlying compute infrastructure using a piece of software called a hypervisor. With virtualization, you create virtual servers (or virtual machines) to run your applications. Your virtual server can have a different operating system than the physical hardware upon which it is running. For the most part, users no longer have to worry whether they have the right operating system, hardware, and networking to support a BI or other application. Virtualization shields users and developers from the underlying complexity of the compute infrastructure (as long as the IT department has created appropriate virtual machines for them to use.)
Deployment Options for Cloud Computing

Public Cloud. Application and compute resources are managed by a third party services provider.
Private Cloud. Application and compute resources are managed by an internal data center team.
Hybrid Cloud. Either a private cloud that leverages the public cloud to handle peak capacity, or a reserved “private” space within a public cloud, or a hybrid architecture in which some components run in a data center and others in the public cloud.