Here's perhaps a better question:
If it's not feasible for a social space to be maintained in some semblance of good order because of its size, should that space even exist?
Do extremely horizontal social networks provide value to society proportional to the harms they seem to cause, and that the people who build them seem either unwilling or unable to stop?
I'd also pose this question about narrowly targeted advertising, which of course goes hand in hand with enabling these platforms to exist.
Things don't necessarily have to exist just because they can.