There are several other software packages with a similar problem. Microsoft SMS is a big one, as well as most McAfee Enterprise Virus scan products.
I think Mark's saying this to conveniently avoid updating his software to work with Windows Vista/Windows 7 =)

So I would love to RTFA to make sure about this, but their high-performance web servers running on FreeBSD jails are down, so I can't...

But here's what I do know. FreeBSD hasn't been a supported OS on ESX Server until vSphere came out less than two weeks ago. That means that either:
A) They were running on the Hosted VMware Server product, whose performance is NOT that impressive (it is a Hosted Virtualization product, not a true Hypervisor)
or B) They were running the unsupported OS on ESX Server, which means there was no VMware Tools available. The drivers included in the Tools package vastly improve things like storage and network performance, which means no wonder their performance stunk.

But moreover, Jails (and other OS-virtualization schemes) are different tools entirely - comparing them to VMware is an apples-to-oranges comparison. Parallels Virtuozzo would be a much more apt comparison.

OS-Virtualization has some performance advantages, for sure. But do you want to run Windows and Linux on the same physical server? Sorry, no luck there, you're virtualizing the OS, not virtual machines. Do you want some of the features like live migration, high availability, and now features like Fault Tolerance? Those don't exist yet. I'm sure they will one day, but today they don't, or at least not with the same level of support that VMware has (or Citrix, Oracle or MS).

If you're a company that's trying to do web hosting, or run lots of very very similar systems that do the same, performance-centric task, then yes! OS Virtualization is for you! If you're like 95% of datacenters out there that have mixed workloads, mixed OS versions, and require deep features that are provided from a real system-level virtualization platform, use those.

Disclosure: I work for a VMware and Microsoft reseller, but I also run Parallels Virtuozzo in our lab, where it does an excellent job of OS-Virtualization on Itanium for multiple SQL servers...

Existing content contributed to Wikipedia was done under the GFDL license, which like the standard GPLv2 includes a "or later version" clause. Wikipedia's license includes this clause.
The latest version of the GFDL now contains a section I think written to specifically allow Wikimedia to do this. See section 11, "Relicensing" here:
http://www.gnu.org/copyleft/fdl.html

For those of you thinking that this is a solution in search of a problem, let me outline where VMware is going with this.
At VMworld this year, Paul Maritz (VMware CEO) outlined their strategy for the future of the desktop - a world where users are given access to applications and data regardless of the end device. Today we see desktops as more device-centric, rather than people centric. VDI (Virtual Desktop Infrastructure) is a step in the direction of device-independence. It doesn't matter if I'm at work, at home, or on the road, I can get to the same desktop, applications, and data.
But going forward VMware is looking at delivering the entire desktop steamed down as a VM to a "client hypervisor", so instead of viewing as it runs remotely in a datacenter, the data is streamed down and processed locally so there's no lag induced by a high-latency link or something like that.
This works great for ordinary PCs or x86-based thin clients. Where VMware is going is taking their hypervisor layer and moving it to the mobile device, so that a user can get their same desktop (or a subset of its functionality) even from their PDA/smartphone. That's the purpose of this technology long term - it's not so you can run Android in a VM on your iPhone.