Its always fun to watch how Commies fail to understand the economy.
Mark Zuckerberg never "lost" that money. His net worth never got that high, it is somewhere around 70 billion right now. Impressive and all, but not the point. Facebook stock went down. This is an entirely different matter than a single person losing any amount of money. Zuckerberg doesn't "own" facebook, that is the entire point of the stocks. His net worth includes all the stock in Facebook he owns, which are now worth less money than before, but not by the billions this thing claims.

Lets put this in a metaphor of a big tower with multiple floors. Zuckerberg made the tower and then sold out the floors to other people, who now built their own stores that make money. If these stores make lots of money, then more people will want to buy the floors and they will thus be worth more money. People who have already bought floors can sell them for more than they are making, and those people can sell to other people, and so on and so forth. Zuckerberg owns a lot of floors that he could sell for a lot of money, or keep the stores on those floors to bring in a decent amount of money. In this case, the tower has become less popular. Less people want to buy it now, and the stores are making less money. So if Zuckerberg wanted to sell his floors, they would be worth less than before. However that money is what the entire tower was worth, not what he owned.

Even if you correct all the math, I think the larger point remains. The wealth inequality between him and the 50th percentile is staggering. Not everything is about communism, EVEN WHEN its posted by Immortal Scientist.