We have very few outages, but they do occur. Service delivery over the internet is generally very reliable, and we have redundant servers and services to enable us to cope if something goes wrong. The 'cloud' involves a number of separate pieces:
Based on past experience we have found the weakest link is the ISP. A typical year sees us have less than four hours of down time, and the failures have mostly been ISP related and have never been our servers.
The four most serious failures of the last ten years have been
We back up the databases several times a day as well as every night. We have two of everything in our network so we can quickly replace a failed component. We have two separate ISPs on completely separate physical networks. We can route around a problem with either one (and have done so twice). Unless someone cuts both cables in the lawn outside our premises we should be safe from losing internet service. Even if that did happen we have access to a facility ten minutes away in another part of the city that will host a server for us short term.
Can your own IT people cope with catastrophe any better?