VMWare and Microsoft.
I think I'm right in saying that Microsoft has bought VMWare and in reference to the sort of ideas about having virtual servers with seconds of downtime is the kind of thing some have suggested microsoft want to do.
Nope, they bought Connectix Virtual PC.
Linux kernel allows for similar functionality and is actually being used in some environments in the way Joel thought (except for the VM snapshots, that's something left to implement, in the mean time we'll just have to wait for another VM to boot). The good thing about it is that Linux inside Linux always runs on any hardware Linux runs on, which removes the hardware replacement problems that Joel thought about. It also provides a very convenient way to develop kernel code without rebooting a lot.
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