shhh
don't tell redhat but I have 336 VMs on an 8-node vmware cluster(16 sockets), with room to grow (their pricing PDF implies I need 30 hosts/60 sockets for 300 VMs.
I figure I could probably get to 500 VMs (384GB/host) with this setup, if I upgrade to 16-core CPUs I may be able to stretch it a bit more..
oh how I love consolidation.