Yup, that's the big issue in my opinion. Their TOS never had research as condition that you accept. When Reddit decided to use their data-set for research and make it available, they had a public blog post explicitly calling it out and had an option to disable your data for research. Naturally I opted out. I was informed of the change and I acted on it. Those users on Facebook never agreed to the research component of the ToS (because it didn't exist yet), did not know they were involved, and were included in a PNAS study that had Cornell researchers involved.