He owns very expensive things and gives away a lot of money, it would be shocking if he does not have significant assets outside of high-value startups and his

He owns very expensive things and gives away a lot of money, it would be shocking if he does not have significant assets outside of high-value startups and his Facebook stock. His pre-existing wealth matters quite a bit with the decision of whether or not to sell out of a position that has been very profitable. Diversification is a fundamental part of wealth management. It's just not smart to have all your eggs in one basket, regardless of what basket that is. Marc already has a lot of baskets, while the hypothetical Facebook engineer does not.