Has twitter been a net negative or a net positive for society overall? Please discuss.
I'd be tempted to say net positive for society overall, based on how it surfaces PoC, women and minorities, and how quickly legitimate news organisations can push breaking news to a large number of people. But I feel its initial creation and subsequent handling is much like Valve and Steam. Both Valve and Twitter (the company) assumed that the majority of its users weren't sociopathic, racist/sexist dicks. And whilst the majority aren't, the signal-to-noise ratio of both Steam Reviews and Twitter is terrible, with automation and lax rule-enforcement ensuring that the awful abusive people have a louder, more harmful effect than the good/nice people having a good effect.
In both cases, the companies involved need to push harder against intolerance and hate, and weather the storms of "Muh free speech", because their reach gives them an outsized influence in today's world. For example, deleting Trump's personal account and suspending the official POTUS account would be nothing but a net positive for (literally) the entire world, and since Twitter is a private company, they have the ability to do that. That they don't means they're abdicating their responsibility to society, and their users.
Facebook, on the other hand, is a lost cause. Its influence, its bubble-effect on users, the ease with which its ads are manipulated... God, you can even go back to its real-name policy to show that no part of the company ever cared about the use of their platform or its effects on society/individuals.