Beyond the initial move to cloud from on-premise infrastructure - many of the customers I speak to are not reliant upon on a single cloud computing provider. The reasons most commonly attributed are resilience and avoiding provider lock-in, but use of differing services to leverage specific services is also a reason to go multi-cloud; and diversity of geographical location can be advantageous depending on the delivery model.
What we do find as counter-point, is that management of these environments can be a challenge due to the difference in security tooling available/compatible with each cloud service - compounded by the specifics of private cloud and remaining on-premise hardware; not only are the traditional controls no longer useable, there isn't a single new set of security rules we can apply across the new environments.
For my contacts, visibility across these environments is extremely important - leading into a common security model that can applied not only to each and every cloud provider, but also those lingering on-premise installations (don't feel bad, we all have them ;-).
Organisations are increasingly using multiple private and public clouds to deploy their applications, in order to avoid vendor lock-in and exploit best-of-breed solutions