The obvious targets are Instagram and WhatsApp, followed by splitting out the ad network, and any other functionality where Facebook unfairly competes with their customers and locks out competition.
WhatsApp & Instagram should be split out not only due to anti-competition, but for the protection of the general public. WhatsApp's founder(s?) walked away from almost $1bn because they couldn't look themselves in the mirror and keep working for Zucky after his blatant lies about not violating peoples' privacy with WhatsApp. That alone warrants investigation, since Money is the only thing Americans care about.
It's not that I'm a fan of Facebook, my usage of it is intentionally minimal and as a company they're appalling, but splitting off WhatsApp would make zero practical difference to the main harms they are perpetrating. It's like splitting off the confectionary stand at an oil company's gas stations. There might be some marginal benefits, sure, but it's not in any way addressing the material issues.
WhatsApp & Instagram should be split out not only due to anti-competition, but for the protection of the general public. WhatsApp's founder(s?) walked away from almost $1bn because they couldn't look themselves in the mirror and keep working for Zucky after his blatant lies about not violating peoples' privacy with WhatsApp. That alone warrants investigation, since Money is the only thing Americans care about.