One downside of the term "cloud computing" being rendered meaningless through overuse is that intelligent people can conduct two entirely different conversations and think they're talking to each other about the same thing. The confusion is now spreading to discussions of cloud brokerages.
Gartner's early (2009) use of the term referred to systems integrators and other third parties who would help their customers negotiate relationships among a variety of cloud vendors. But recent buzz has refashioned the "broker" concept as a sort of commodities trader, aggregating raw computing power and creating spot markets. It may be intellectually interesting to consider the feasibility of multiple public cloud infrastructure providers standardizing to the point where computing power could flow, frictionlessly, between data centers. And the OpenStack initiative would be a good prerequisite to achieving this sort of liquidity.
But suddenly we've started talking about infrastructure-as-a-service (IaaS). There's nothing wrong with IaaS - I'm a big fan, and my company's products all run on Amazon Web Services - but to me IaaS is the least interesting layer of the cloud computing stack, at least from an enterprise business perspective.