Organizations often fall into new technologies haphazardly. Different groups discover new ways of working that better meet their needs, and they go for it. Eventually, CIOs find themselves with something of a jumble to manage.
Cloud is a particularly extreme example of this, as cloud services can be quite easy to sign onto. There are certainly categories of cloud services that CIOs don't need to control -- things that are opportunistic, department-specific and that don't need to link into core systems or data. As long as the acquiring business people understand and abide by some basic guidelines (mainly having to do with security), let a thousand flowers bloom.
However, when an organization starts to look to cloud for its enterprise IT needs, that's a very different story.