Earlier this week, he sold shares amounting to nearly $300 million.
Although the sale wasn't discretionary and was just meant to pay off the taxes on stock Koum received after selling his company, that's a lot of money (and makes the ~$160 million Marc Andreessen just sold look like small potatoes).
But it's even more interesting in light of Koum's rags-to-riches history.
Here's how Koum got where he is today:
