There is a difference between a service outages, which do happen and are unavoidable no matter who builds your system, and actually losing permanent data. Which is Amazon does guarantee only 99.95% uptime.

There is a difference in a discussion about trusting the Cloud with your data and services between it going down briefly on occasion (somewhat acceptable, within very narrow limits) and actually losing data or longterm traffic because of a service failure. Seriously breaching the SLA causes compensation as well as a big loss of reputation and business, going down for a couple hours once a year is hardly the type of instability that would terrify most online businesses, nor is it something that individual companies are able to avoid themselves.