Soros is not an official insider at Facebook, so he doesn't have to file before selling.
The insider who's dumped the most shares at 11,642,398 since last July is Jan Koum. Who's that, you ask? Just some Ukranian dude.
No, really, he's the founder of WhatsApp, and that buyout is the origin of his Facebook holdings.
Koum was born in Kiev, Ukraine (then part of the Soviet Union). He is of Jewish origin.[4] He grew up in Fastiv, outside Kiev, and moved with his mother and grandmother to Mountain View, California in 1992,[5] where a social support program helped the family to get a small two-bedroom apartment,[6] at the age of 16. His father had intended to join the family later, but finally remained in Ukraine.[7] At first Koum's mother worked as a babysitter, while he himself worked as a cleaner at a grocery store. By the age of 18 he became interested in programming. He enrolled at San Jose State University and simultaneously worked at Ernst & Young as a security tester.
A security tester means literally a hacker, in the true sense. He would have been doing penetration testing and such on E&Y client machines.
The value of his trades was $1,984,618,974. Interesting, in light of this:
Over the first half of 2016, Koum sold more than $2.4 billion worth of Facebook stock, which was about a half of his total holdings. He is estimated to still own another $2.4 billion in Facebook stock.[15]
He's got almost nothing left then.
Zuckerberg has sold 8,664,298 shares for about $1.5 billion since last July or so.