Exchange 2013 in Public Cloud

HI,
In a shared environment virtualized either Hyper-v or vmware, defined as IaaS (Public Cloud). It is possible to build a platform Exchange 2010/2013.
The deployment of the Exchange servers in virtual machines production Windows Azure does not support. Does this extend to all shared virtualized platform?
The majority of the information refers to dedicated virtualized environment, but not shared.
The idea is to clarify this type of platform or definitely should lead to a SaaS environment as Exchange Multi-Tenant.

Regards,
Miguel