This paper on Cloud Computing by CA provides some good solid descriptions of the role of a Cloud Gateway "for IT management facets such as Service Management, Data Center Automation, Application Performance Management, Security Management, and Infrastructure Management to extend the traditional IT management stack". It is a good approach to providing an infrastructural approach to managing usage of Cloud-based services, rather than baking this management into the applications themselves. Overlaying management infrastructure on top of application is, of course, a key aspect of what CA does, so it's not a surprise that this is where they see added value.

The same paper also includes this history of Cloud Computing, which takes the "timesharing" analogy. [ Note, an alternative approach is to see Cloud Computing as an extension of outsourcing, or to see it in terms of object re-use. As with all successful IT trends, like success in general, it has "many fathers"].

A Brief History of Cloud Computing

Despite its new-found prominence today,
cloud computing is not a new concept. In
fact, its roots can be traced back to the
early sixties. In January 1959, John Mc-
Carthy predicted that advances in timesharing
technology would lead to an
ultimate direction in computing, where
computing power would be sold as a utility
similar to water or electricity. This idea
was summarized in memorandum he sent
to MIT Professor P. M. Morse on January
1, 1959:
“This memorandum is based on the assumption
that MIT will be given a transistorized
IBM 709 about July 1960. I want
to propose an operating system for it that
will substantially reduce the time required
to get a problem solved on the machine....
The proposal requires a complete
revision in the way the machine is used....I
think the proposal points to the way all
computers will be operated in the future,
and we have a chance to pioneer a big
step forward in the way computers are
used....” *
In 1961, to mark its centennial anniversary,
MIT (Massachusetts Institute of
Technology) organized a series of lectures
on the future of computing. In one of the
lectures Morse publically voiced his idea.
However, his idea never really developed
given the technology constraints at that
time.
With the Internet offering a significant
bandwidth in the nineties, the cloud computing
concept started making the rounds
again. With the introduction of Salesforce.
com in 1999, it finally arrived with
full thrust. The next big step was Amazon
Web Services in 2002. In 2006, Amazon
launched its Elastic Compute Cloud aka
EC2 as a commercial service, offering
computers on rent. This was the first
widely used cloud computing service. And
since then the world has never been the
same again... cloud computing had finally
arrived!
http://www.ca.com/Files/TechnicalDocuments/ca-technology-exchange_233637.pdf

Also in the same paper has a useful taxonomy of actors in the Cloud infrastructure area:

...based on the Service type, cloud services can be classified into
the following areas:

Cloud Service Provider (CSP):
Organizations that offer the services
(computing services, application services, etc.) for consumption through
a well-defined set of interfaces based on an agreed cost model (for example,
Amazon EC2).

Cloud Service Consumer (CSC):
Consumers that use computing services
provided by a CSP through a well-defined set of interfaces. For example,
cloud services provided by CA Clarity PPM On Demand could be used for
project planning and management without deploying the software inpremises.
Similarly Amazon EC2 services could be utilized by consumers
to handle peak computing load. In this case, the computing resources are
provisioned into Amazon EC2. Once the load returns to normal level these resources could be de-provisioned.

Cloud Broker/Federator:
Organizations that combine multiple trustworthy
services from different CSPs to provide a new computing service, essentially
adding value to improve on specific capabilities. For example, a
broker may combine storage services from one vendor with the identity
and access management services from another vendor to provide rolebased
storage secure storage services (for example, Vordel Cloud Service
Broker).