The Exchange product group has announced support for putting your Exchange 2013 File Share Witness (FSW) server in Azure.
I think this is the next big advancement with the marriage of Exchange and the cloud. Yes you can migrate to O365 and leverage all of the integration with: Exchange, Lync, SharePoint, OneDrive, and Skype. While some organizations do have the expertise in house to support all of these products, some companies do not. O365 can certainly help deploy quickly a myriad of technologies and applications with minimal engineer investment.
I’ve run into several companies that would like to leverage the built in ability of High Availability (HA) and Site Resilience within Exchange 2013 deployed on premises. Some of these companies, however are limited in options, as they only have two datacenters they can leverage. It is recommended to place your FSW server in a separate 3rd datacenter, which is on the outside looking in at the other two datacenters where your DAG members are deployed. The FSW can then maintain Exchange functionality automagically with no human intervention.
We knew this was coming and now it’s here. Just a reminder, there are no plans to back port this option to Exchange 2010. The main reason being that the FSW server in 2010 is to be in the same AD site as DAG members, and since spreading your DAG into the cloud is not yet supported for Exchange, you’ll need to keep a 2010 FSW on premises.