The ownership percentages listed on the site only sum to 72.669%, so there's a lot of stock not accounted for. I'd imagine that there are lots of relatively low-profile employees with 7-8 figure stakes of that dark 27.331%.
I think I read in different places that the option pool for a startup is usually around 10-15%. So assuming those guys on the list are not part of it, and FB allocated half of it to employees, that is nearly 4B (at a 80B valuation). If you split that evenly between 2000 employees that is $2M per employee. Ok, I know my math gots to be wrong. Can someone help?
Actually, that's not too far off. If you were hired pre-2010 your stock is probably worth > $1 million by now. That goes up by some constant multiple for every year previous to that.