Numerous articles discuss the recent security failure of Dropbox (like this one). The linked article even mentions that this may cause users to question the security of the company used to store all of their files in the cloud. I think the greater concern is: do users trust any service or product provider to store all of their files?
Most consumers trust Apple or Dell or HP to store their files on the hard drives of computers they buy. Likewise the same question should be asked when it comes to email services, to web-sites that store credit card numbers, to services that sell music and videos, etc. Everything a computer user has that generates or uses some kind of data needs to have a security context. For most users security is never thought of and maybe the Dropbox incident will get them to think about it but I doubt it.
Likewise in the enterprise the servers processes run on, the arrays of disks that store corporate data, the network that allows software and services (and SaaS) to function all need to have a security context. Security doesn't all of the sudden become an issue when there is a cloud provider.
All computer systems have a level of trust between the provider of the system (hardware, software, service, etc.) and the user even if clouds are not involved.
