Everyone loves a good buzz word. All too often, this love affair leads to assumptions and misplaced trust and we all have heard about what happens when you assume.
Last month, a code hosting and project management service provider was forced to shut down because of failure to use common sense. They advertised full redundancy and kept not only client information in their Amazon EC2 cloud but also backups of that same information. Unfortunately it seems they did not have redundant backups stored elsewhere. While Amazon's EC2 services protected them (as expected) from random failure, they were not protected when attackers hacked into their accounts and, after a failure to extort money, proceeded to delete their various client snapshots, SVN and GIT repositories, server instances and other critical data and backups.
Like any other service, putting something into "the cloud" has its benefits but should never be considered the silver bullet to resolve all of your worries.