When is an incident a tsunami, and when does it only rattle the crockery?

When an earthquake occurs we all know it’s severity because its size is reported using the Richter scale. However, when an Information Technology major incident occurs, there is no scale and the size of the incident is subjective. Was the Internet outage in the Middle East really big? Now wouldn’t it be a good idea if a scale existed that measured the major incidents and classified them appropriately. We could then state that this one was a tsunami while another one might only have rattled the crockery.

My opinion is that the answer lies in an Incident User Metric. The metric is based on the number of people affected and the opportunity costs associated with the impact to productivity. Practically, this is not too difficult and reasonable estimates can be made to the impacted population and productivity loss. However, any other comparative mechanism could be appropriate. Any clever ideas on a scale?