Milton Friedman once said "Only a crisis, actual or perceived, produces real change. When that crisis occurs, the actions that are taken depend on the ideas that are lying around. That, I believe, is our basic function; to develop alternatives to existing policies, to keep them alive and available until the politically impossible becomes politically inevitable.”
The idea of cloud computing has been bubbling away for a few years now. Many CIOs have watched but not acted, for a number of reasons. One reason may be personnel. If your team is entrenched in the behaviours and solutions of an on-premise world the change management exercise for the IT team, let alone the organisation would take cloud computing off the agenda. To tell your CEO that he will be using his favourite PC application on the browser, ditto. The decoupling of systems intertwined in the on-premise world, don't go there. There are many reasons why cloud computing may be politically impossible.