I have no idea how this will work, and I'm once again glad that I don't use Instagram... but I know a lot of people who do, and many of those people are celebrities to some degree.
Here's what I'm wondering: if Kaley Cuoco uses Instagram to share a photo of her and Melissa Rauch doing something silly, does that mean that Instagram can take that photo and use it to advertise for something silly without compensating them for what becomes a use of their likeness for commercial purposes? I can see that being a pretty serious shitstorm if it happens.
This sort of dovetails with another concern I have about the automatic opt-in nature of much of our digital life: if I'm in someone's address book, and they use an app that grants the developer full, unfettered access to their address book, I've now had my information given without my consultation or consent to a developer, and I never even knew it was happening.
Just as we have a "do not track" option for our webbrowsing habits, we're going to need to have something similar for other aspects of our increasingly-digital lives: from contact information to our location to moving and still images of ourselves. Because it's no long enough for me to be careful with my opt-ins and online sharing; now I have to ensure that every single person around me is careful, as well.