I had a colleague of mine comment in a meeting that SQL Server 2014 supports cross-domain data synchronisation using AlwaysOn Availability Groups. I didn't contradict that immediately because, even though I thought it wasn't the case, I couldn't find any documentation either confirming or denying it.
Looking at the Network Access section for troubleshooting AlwaysOn AG (http://msdn.microsoft.com/en-us/library/ff878308.aspx#NetworkAccess), the inference is that you can have AlwaysOn AG spanning different domains. However, one of the pre-requisities for creating a WSFC is that all servers that are to be added as cluster nodes are joined to the same Active Directory domain (http://technet.microsoft.com/en-us/library/dn505754.aspx).
So I guess the question is - can you have a cross-domain implementation of AlwaysOn AG? And if so, how?