As everyone else said, you could not use the cloud for illegal activities or you could be both criminally and civilly liable. And, it's not so hard to be caught when dealing over the internet, no matter how well you think you are protected. A number of things might be prohibited when it comes to online cloud computing/hosting.
For instance, hosting spoof pages which attempt to trick the user into providing sensitive details that are then used for malicious purposes such as identity theft would be forbidden.
However, for regular site hosting you should do well just by hosting your site (assuming it has acceptable content) and will have no issues with your cloud hosting provider.