The notion of a Cloud Broker is a new and interesting topic and I believe it is something which will be talked about increasingly frequently in the near future. If you don't believe me, the folks over at Gartner have discussed the importance of this role in the cloud computing space:
"The future of cloud computing will be permeated with the notion of brokers negotiating relationships between providers of cloud services and the service customers. [...] Enhancement will include managing access to these services, providing greater security or even creating completely new services." -- Frank Kenney
Given that they are going to prove to be important, its probably worthwhile to take the time and discuss what it is that these cloud brokers actually do. In my eyes, cloud brokers are an abstraction layer between the end user and the many cloud services at their disposal. While this notion could be applied in many different contexts, when I say cloud services I am referring to Infrastructure-as-a-Service providers (e.g. Amazon, Rackspace, GoGrid, Joynet). With a plethora of cloud providers, each with a their own API/set of services/pricing model/etc it would be quite cumbersome for the end-user to programmatically access each service. Instead, the cloud broker creates the layer of abstraction between the user and providers so that the end users can see one cohesive view of all of the services. This way the customer doesn't have to worry about the nitty gritty like the different REST calls required to create a server, they just hit the launch button and a server appears on the desired cloud. This is roughly the state of cloud brokering today from companies like RightScale, CloudKick, and Elastra (give or take a little bit). Yes, there is some work left to do by these vendors to support more clouds but its only a matter of time before they have most of their bases covered.
While that is the current state of affairs, the future of cloud brokers is something that is a lot more murky (at least in my mind). I think one of the big ideas that many people have for cloud brokers is that they are going to become these intelligent tools which the user tells what they want and then it figures out the best way to do that for them. So if I need a server and I need it now (at whatever it costs) then it will pick the appropriate cloud. Similarly, if I just want a server at some point this week but I want it cheap then it will wait around until it finds a good deal and then starts up that server for me.
On the surface that seems all honkey dorey but in practice there are two really big issues with delivering such a vision. The first is transparency. Any time you are making an intelligent system which is making decisions on behalf of the user, it is absolutely critical that the decision making process be completely transparent to the end user. There are a lot of contexts where transparency is not terribly important (e.g. search results), but the second a users credit card is being charged the game changes in a big way. It is almost guaranteed that at some point you will get angry customers calling in asking why at some point your system made decision X where they expected decision Y. This is not the time to start having to explain the nuances of your cost-based least squares weighted estimation algorithmic ridiculousness. You might even try to be tricky and come up with some metric which is an amalgamation of a ton of different factors into one nice number scale (e.g. "Our system computed a doodle factor of 8.3 and as a result launched a new server"). While having that one number to point at is a nice trick, it generally does little to hide the formula that is used to compute it which inevitably becomes filled with unexplainable magic numbers. I believe that the result of this is going to be extremely simple systems which instead of trying to make the complex decisions are going to do their best to present the user with as much relevant information as possible and allow them to make the decision. If you imagine the case where the user wants a server very quickly one could imagine a system presenting you with the current cost and average boot time of a server across each of the clouds and then allowing the user to decide. The money vs speed trade-off is a complex decision and ultimately it is only the user who really knows how much they are willing to trade for one or the other.
The other major issue I see with these systems is that without variable pricing the utility of the intelligent system decreases greatly. As far as I know there are no cloud vendor out there changing their prices each day/hour/minute in order to account for changes in supply vs demand. While an interesting option and one any economist would be proud of, I think that vendors have moved away from this model as a result of the lack of transparency. What was once the brain-dead simple 10 cents an hour now becomes a decision requiring a lot more consideration. How much does it cost now? Well do I really need it now? If I wait will it get cheaper? And so on. Eventually I think a someone will try to do something along these lines and while I'm not a huge fan of the idea I wish them the best of luck. Getting back to the original point, until we start seeing clouds employing truly dynamic pricing the idea of having an intelligent system making decisions for me becomes a lot less necessary.
Ultimately I think the cloud broker space is one that is going to grow into many areas and service many niche markets. However as it continues to grow, don't be surprised as they all continue to keep a pole's length distance between themselves and the all knowing sentient system of doom.