Hi Geeba,
VMware has disabled this function due to the Apple EULA that must be agreed when installing OSX. Although yes it IS technically possible, Apple wish to keep hold of which hardware can / can't run their software.
As you are probably aware the Apple X-Serve has been placed on the HCL for ESXi5 (http://www.vmware.com/resources/compatibility/detail.php?deviceCategory=server&productid=20234&devic...) This is the only hardware that is able to run OSX as VMs, that is unless you run VMware Fusion on an Apple desktop / laptop.
Cheers,
Book - Mastering VMware vSphere 5.5
Blog - LabGuides.com & NickMarshall.com.au
Podcast - vBrownBag.com
