The cloud computing model, as you probably know, is the movement of computing services and resources from the desktop or from a system of computers within a corporate network to the public Internet. If the operators of those services don't have the confidence that the materials they're storing on behalf of somebody else can be stored by them at the discretion of that somebody else without triggering liability, then they just won't do it.
In other words, you have to have a certain level of immunity as the operator of a service on behalf of the end client. The end clients should be liable for whatever they're doing and whatever they're storing, but ultimately cloud computing is only going to work as a system of computing if the people who are operating and investing in the services have the confidence that those services themselves aren't going to come under attack by virtue of what their customers are doing.