It's not actually 57% of facebook's value (since that would make him by far the richest person).. It's voting rights. Facebook stock is split into 2 classes.. I think monetary value wise, he holds a much smaller chunk of FB. Same for Larry Page/Sergey Brin for Google.
Rather than percentages, the median/mode of absolute monetary value would be more useful, since that gives you a directly number you can compare to non-VC startup (lifestyle startup). If you own 2% of a 100M VC startup, maybe it's the same to fully own a 2M fully owned lifestyle startup.
Both monetary value and voting rights would be useful metrics, since different founders care about different things. Zuckerberg is absolutely obsessed with retaining control of his company, even at a significant cost to his net worth.
On a side note, I was like "wait a second, 2M is now considered a lifestyle business?" but then I remembered that crazy P/E is the norm around here, so a valuation of 2M probably means that the founder subsists on ramen... :(
Crazy P/E is the market outcome in any low interest rate environment. If an investor wants to get 2% over the safe (read: government bonds) rate of return and the safe rate is 4%, then the investor wants a 6% return and that gives you price/profit ratio (not quite the same as P/E, I know, but for purposes of lifestyle business income this is the relevant number anyway of about 16).
If the safe rate is 0%, then the investor is willing to settle for a 2% return and you get a price/profit ratio of 50. Given identical profits that means 3x the valuation.
In real life this is a bit more complicated, because investors may not necessarily seek a simple additive percentage on top of the safe rate of return, but the same dynamic plays out in general.
Or to put another way, say you have a lifestyle business with $100k/year of profit. That's nothing too special. What valuation should that correspond to? Depends on risk, of course, but $1-2M doesn't seem unreasonable; that corresponds to 5-10% annual return, which is pretty good right now.
Rather than percentages, the median/mode of absolute monetary value would be more useful, since that gives you a directly number you can compare to non-VC startup (lifestyle startup). If you own 2% of a 100M VC startup, maybe it's the same to fully own a 2M fully owned lifestyle startup.