Cloud computing promises dramatic savings -- if downtime is kept in check

The value of any form of hosting needs always to be qualified with "(to the degree that) downtime is kept in check.

The tricky part is getting an accurate assessment of likelihood and severity of downtime. Who's going to do that assessment? I don't think I want to ask my cloud provider about his reliability, my internal IT manager about his, and then enter their numbers into my decision tree.

What about internal(within your IT dept) backup for a cloud-based operation? I'd like to know how Hackers cope with the relative risks.