[akamia]

I think you need to clarify what you mean by at rest. You mention browser history but it's not clear to me if you mean that it's encrypted in the browser. If you mean it's encrypted within your data store on your servers, that's great for security but doesn't really address the ad concern. I'm assuming you hold the encryption keys. If that's the case, you can decrypt the users' data in your data store for ad targeting purposes.

[jstrafy]

In terms of the ad concern, through our choices we have already made that inconvenient to do. At the moment we do hold the encryption keys, but as privacy seems to be a great concern (as we expected it to be) we will continue to push forward our practices on privacy.

So to be clear, anything you share on Circles is encrypted in transit with SSL/TLS, then encrypted at rest on our servers, to which we currently (but hopefully not for long) hold the keys.