5. First Amendment limitations on private companies?
If people think that Twitter is a place for free and open discussion, but that is NOT the case, then it would be harmful to their reputation. I actually think that one of the main events in the history of Twitter's growth was their prominent position during the ruckus after the Iranian election a couple of years ago. The Iranian government would certainly approve if Twitter is free of such nuisances as the First Amendment.
Freedom. It's about meaningful and unconstrained choice, not beer.