This might come as a surprise[^fn1], but Thomas’ analysis makes it sound like Google might be the most protective of photographer’s rights:
> Google+’s TOS tends to provide photographers greater protection with a provision that your content there can be used for the “limited purpose of operating, promoting and improving our services, and to develop new ones.” Nothing about selling off your photos to third parties there, folks.
I am going to have to dig into these before I make my decision on what my “new Instagram” will be.
[^fn1]: A surprise because of Google’s reputation regarding privacy.