Successful communications networks are going to work when you can get as many people as possible to participate. Cloud oriented communications infrastructures are designed to allow mass participation and involve as many people as possible. This is what drives successful communications systems such as telephone and email to be interconnected. Delivering the communication as a service to everyone's home or office or pocket keeps the costs down for the end user, the efficiency of the shared system up, and participation barriers to entry so low that nearly everyone can be a participant.
Consider the following examples: Email communications are successfully delivered as a service by AOL, Yahoo, Google, Hotmail, and more. Instant Messaging communications are successfully delivered as a service by AOL, Yahoo, MSN, Google, Skype, and more. Social networks communications services are successfully delivered as a service by twitter and facebook, and more. In these cases, they are usually a single system providing the service, costs to participate are very low or nothing, and since the systems are so ubiquitous, it is convenient to communication with nearly anyone.
Communications are best when delivered as a service. So, it should be no surprise to find that the most successful software as a service applications have a significant communications element to them…because it is a natural fit and an appropriate way of delivering communications.