Any information or content that you voluntarily disclose for posting to the Service, such as User Content, becomes available to the public, as controlled by any applicable privacy settings that you set." [Emphasis added]
Thus neither directly promises that private photos will remain private. Instead, your privacy on Instagram is subject to future changes in the privacy settings options.
As you may recall, Facebook has, on a few occasions, adjusted privacy settings in ways that meant your ability to keep some information private was no longer available. These sorts of privacy downgrades have been met with quite a bit of criticism from users. Hopefully, Instagram will learn from that experience and refrain from removing privacy settings.
The new terms are scheduled to take effect on January 19, 2012 — which means Instagram still has time to get this right.
- 1. Instagram was purchased by Facebook earlier this year.