I don't have direct experience here with support. We run SQLServerCentral as a cluster on virtual machines (Not AG/AlwaysOn) with 2008. Both nodes are provided to us by our hosting provider, and we validate the cluster inside this. I have some friends that have done this as well and I'm sure they have support as they are larger Fortune 1000 companies that typically require this.

I would assume this would be supported for SS2K12/W2k12 as well. My guess is they support hyper-v and VMWare, but it's possible they don't want something Xen or Virtual box.

They do list virtual machines in the TechNet articles (sample: http://technet.microsoft.com/en-us/library/hh831414.aspx), but I'd put a call into MS to verify this for your org.