Timely blog posts for the WIN! This came up at the office today, that is to say, is running Exchange in a VM a good idea? The general consensus was that "YES” it is. You see those quotes there, they’re significant. That is not to blanketly say that running a massive Exchange deployment in a VM (or VM’s) is ok. There will need to be some intelligent design and engineering around this, but it is entirely possible, and if done right, can outperform your physical deployment.
That said, Mike Laverick at RTFM-Ed posted some examples today that YES it can be, and is being done.