One physical DC still recommended?

Hello,

a few years ago (Windows 2008R2) somebody told me, that it is recommended to have at least one Domain Controller as a physical server.
This server should be responsible for the FSMO roles and for the time sync in the domain. Also complete virtualized ADDS Environments wouldn't be supported by Microsoft.

With Windows 2012, is that still a recommendation? Will I get support from Microsoft in a completely virtualized ADDS forests?

Thanks for your help

Andre