People love to talk about great the web of the 90's was, and I miss it myself, but what made it work was "the price of admission" which elevated the level of both the posters (who had to understand how to make, and pay for, a web site), and the readers (who had to pay for an internet connection, and understand how to configure the connection). I think categorizing social media services as common carriers is half of it. People who shipped things over the rail line also paid money for the service. I think social media services should charge a nominal fee for the privilege of posting. This alone would keep out a lot of the spammy riff-raff, and would automatically help in taking some pressure off the moderation algorithms and content screeners. If it were up to me, I'd put limits on how large of an enterprise would be allowed to be supported with ad tech.