As seen during the Sandy hurricane, the real clouds brought distruction to many web hosting providers.
This long thread on Webhostingtalk just shows how many of the hosting providers were affected. http://www.webhostingtalk.com/showthread.php?t=1205042
But the good news is that, datacenters that took great advanced preparations were not affected.
And the websites that are on virtual clouds spread accross different data centers also were not affected