Meh. I'm not convinced of 'cloud'.
Partly because theres a vagueness and variety in what people think it should mean (I think the US gov do actually have some definitions but the commerical/public perception varies)
But if we assume cloud means virtualisation with redundancy then there are alternative ways to offer segregation, security and consolidation without virtualisation.
I'm not a hugely massive fan of adding an extra layer of complexity into any design.