Who owns what we post?
So shouldn’t some of the legal repercussions be shared with whomever “owns” what I post?
Generally you own what you post, but you have given a license to the site to display and use it. In the US, social media sites are protected by something called Section 230. This allows sites to display user-generated content without being liable for legal issues related to it, as long as they do a decent job of trying to moderate clearly illegal content.