What is the impact of virtualization on high volume websites?

I’ll admit right now that I struggle with the “virtualization everything” move that has taken place over the past few years, mainly because I like the predictability of raw hardware and the thought of “one big server” makes me a little nervous. I came across this http://www.webperformanceinc.com/library/reports/LoadTestingVirtualizationPerformance/index.html report which clearly shows the trade off you make between performance and manageability when you host even a simple web application in a virtualized environment. Definitely some food for thought!