At the office we're building a whole new virtual environment and I currently have 9 VM's running in VSphere (Vcenter) on a Nexsan with plans to almost double that by the time we're done.
At home, on the iMac, with Vmware Fusion 7 I only have two VM's, Windows 8.1 and Windows 10 (Technical Preview). I do not run them at the same time, only one at a time.