Talking further about in his blog post, Kevin stated that Instagram users are only owners of their photos. They are completely independent to set the privacy status to their pictures, that they desire. They can set it Private or Public. Instagram has nothing to decide it here and this decision is solely of user.
We respect that there are creative artists and hobbyists out there alike that pour their heart into production of beautiful photos, and we admit that your photos are your photos.
Kevin stated on it:
Our intention for updating the TOS was to communicate with everyone that we would like to experiment with innovative advertising that looks right on Instagram platform.