I know I sound like the NSA shill here but I agree with this 100%. Stuff I've allowed to be on G+ or FB is done with the full knowledge that even the "Restricted" settings will not 100% reliably stop it from leaking to the Internet. Even without the NSA there are problems with corporate insiders, hackers, implementation bugs, countless other things.
Data I have that needs to be private is not stored anywhere on any cloud, except perhaps in an encrypted format sufficient for Data-at-rest.
In fact I was looking for a cloud service provider to use for some work-related stuff (PII) when I came to the conclusion that I couldn't actually trust any of the available cloud services, since it would always be possible for a cloud provider to gain physical access to the machine even if I use full-disk encryption.
What I'm hoping is that someday providers like Heroku will kind of meet-in-the-middle and setup a provision for setting up an enterprise cloud service (inside the protected WAN) that can be provisioned and managed similar to the public cloud SaaS services. Something where the enterprise would have the hardware and network interfaces but Heroku would provide the OS and management software.