Well, you can't completely understand the calls for breakup until you understand that the politicians don't really care about the traditional monopoly issues. They're upset that Facebook, Google, and Twitter have as much control over the political discourse as they do (note the missing Amazon in that list, modulo the fact that Amazon's CEO happens to own a major newspaper). If society is like a big collective brain as it thinks about the big issues, those companies have installed filters on a significant portion of the neural links and they aggressively use them.

I personally think this is a bad thing as well, and fully support breaking them up for this reason alone. In a perfect world, we'd carefully and thoughtfully craft new laws to address this matter; in reality, we're going to probably "creatively" read some existing laws in new and unpredictable ways to get some unprincipled compromise of what several groups want.

So I'm likely to be both unhappy at the theory and the practice of how they are actually broken up. Isn't government fun. But I do agree they need to be broken up.

This analysis is then useful as a conventional reading of anti-trust laws, but I fully expect that if a conventional reading of the laws won't get it done, then either new laws are going to be made or unconventional readings will be made.

I also think that these platforms are basically boned in terms of voters and public opinion. Consider two sets of forces on these platforms: First, the set of forces that want to insist that they carry any given piece of speech, and second, the forces that want to insist that they censor any given piece of speech. (Observe I'm not breaking this up on conventional political lines; all sides have their lists of both types of things they want.) I submit that there simply is no solution for a single universal platform that combines all of them. Almost all even remotely controversial speech is going to be on the mandatory list from one party and the banned list from another, which means that in the public opinion war, every political side is going to have an endless list of grievances against these platforms, literally no matter what they do. There is no solution for platforms at this scale. This is ultimately what is going to kill them; even if the government doesn't break them apart, something will.

In fact, in my first paragraph, when I said they "aggressively use" the filters, I'm not saying they even necessarily have a choice, or particularly accusing them of "incorrect" usage. I think at this point, they're simply at a size where they're boned no matter what they do with those filters. I do have my own list of particular localized grievances, but if you don't have one now, you probably will soon. The latest YouTube demonetization purge is hitting a lot of weird channels, including... a channel dedicated to making completely a-political cartoon parodies of the Final Fantasy games? Everyone's going to be pissed at something. I don't think there's ultimately a solution to "the one big site that everyone uses". Applications to the stock price of the relevant entities left as an exercise for the reader.