If you read about the theoretical foundations behind the different methods to interconnect applications, you will no doubt hear challenges to a message broker's ability to scale (especially coming from Enterprise Service Bus vendors).  This is most likely because they use examples of non-scalable brokers to prove their point.  We could do that too with almost any technology - take a faulty implementation, make the assumption that its design is the only possible way to implement the technology and then generalize until as much as necessary to "prove" that the principle (theory) is flawed, but we won't.  Instead, we will consider the claim itself ("brokers are not scalable") in more detail and see why its foundation is not sturdy.(Click article title to read more)