Make Three Fault Domains the minimum configuration of an Availability Set
When deploying SQL Server AlwaysOn AG or FCI for high availability, you need to ensure that you always have a majority of cluster votes online. In order to do this you need to ensure that each cluster node and the file share witness reside in different fault domains. A two node cluster needs a minimum of three Fault Domains. However, Azure currently only guarantees two Fault Domains per Availability Set. This is inadequate due to the fact that the failure of a single Fault Domain will bring down your entire cluster if two of cluster votes reside in that Fault Domain. It is impossible to deploy highly available SQL Server without ensuring each cluster vote resides in a different Fault Domain, which means a minimum of three are needed.
David Bermingham commented
Good news, in Azure Resource Manager deployments you get three fault domains by default now. Any chance this will be back ported to Azure Classic while the kinks are work out of ARM?
You have my majority of cluster votes online!