Ian Rae has written an interesting piece asking "Is cloud computing stable in bad weather?" , Below are my comments.
Ian your post reads like the doom and gloom forecasts we saw about cloud computing back in 2007. Cloud computing is as much about trust as it is about efficiency. The real question you should be asking is do I trust microsoft, amazon or even AT&T to mange my infrastructure better then an internal data center team, and in my rather bias opinion the answer for the most part is yes.
Also, about your comment on outages, the question isn't will the cloud provider go down, because it certainly will. The real question is how do I enable a hybrid cloud environment that assumes failure and can do so gracefully. (This one of my main motivators for a unified cloud interface standard)
Lastly, as some one who has built a business on the so called private cloud platform. The idea of a quarantined shared internal cloud, aka private cloud is an oxymoron. Cloud computing is about using resources where ever and when ever, internally or externally.