I can control who I share my photos with, but once I share the photo I lose control of it. Those I have shared the photo with can tag the photo and share the photo with others. Anyone the photo is shared with can also see who else the photo is shared with, and anyone who is tagged in a photo will receive a notification and be able to see both the photo, and the related album it is a part of.

Photos from an iPhone

Google+ Photos does not have the same as it does from an Android smartphone, but I can still use the Google+ app on the iPhone to my advantage.

The photos I take on the iPhone don't get uploaded to Google+, but I can either post photos from the iPhone photo library to Google+, or take photos from within the Google+ app that are then posted to the social network.

I can choose which Circles to share the photo with, so I created an empty Circle called "iPhone Photos". By posting photos to the "iPhone Photos" Circle, I am uploading them to Google+ and adding the pictures to my Google+ Photos albums (and--by extension--Picasa) without actually sharing them with anyone. It also gives me that same benefit of having a backup of my photos in the event that my iPhone is lost or stolen.