Note that Oracle is nowhere to be found. It is possible that OVM is buried in Citrix's paltry 8%. (OVM is a Xen variant after all.) Having said that, it is the case that at least from a virtualization standpoint, Oracle has yet to gain any significant momentum, and VMware remains the incumbent majority marketshare leader.
Re: IDC Virtualization Market Share Study Fails to Mention Oracle
Oracle has been behind the curve on virtualizing. Their stance on puting on their virtualizing brakes is most likely a ploy allowing them to get their act together. I will assume we'll see their piece of the pie increase by year's end.
What surprised me is Microsoft's Hyper-V momentum.