You need to remember one thing, T&C's are not worth the paper or digital space they are written in because time after time they get challenged and lose. T&C's are there to scare users into doing things and not doing things. Also, this thing about a social media company can do what ever they want with what a person posts, no they cannot. Again there are videos on youtube where people have taken Facebook and Instagram to court for using images of a persons profile and using it in commercial applications. A company may claim they can use what you post but as soon as they try to make money of what you post, nope, not going to happen. I remember watching a youtube channel of a photography couple who would post tutorial videos on youtube and post their photo's on Instagram and they notice their photo's were being used by some of Intagrams 'partners/vendors' for commercial gain. The couple would takes these companies to court and guess what, they would win because the judges would say that whilst the T&C's may grant companies a right to use a user pictures, they do not have the right to use them for monetary gain without getting permission from the owners of the work.