If your cloud services relay on a data center which is in an area affected by a natural disaster and your users or home office is not, you probably look at the recent disaster in Japan as a negative for cloud-based services. the reality is however that once your services are in the cloud, you will be able to more easily have access to computing resources which are geographically dispersed.

Moreover, generally speaking, a data center is more resilient to natural disasters than a typical office would be. This is the case for example with the Terremark building in Miami, FL which while located in a hurricane zone, is one of the most disaster-proof structures you will find. This is likely why the US government virtually owns an entire floor of the building and moreover why Verizon decided to buy the company as it expands its cloud strategy.

Larry Dignan has more analysis on the topic at ZDnet and its worth a read.