Well, a billion is a lot of walking around money. If he just cashed out for no particular reason, it would point to a lack of faith in the growth prospects for Facebook. After all if you owned a billion dollars of a stock that you thought was a rocketship, wouldn't you leave it in and turn it into five or ten billion?
Of could it could be he wanted to spread his risk around, or pay his taxes.
Not if you don't care anything about the stock price or money. He just made 1.13 bln dollars for his company. If he invests it directly in fb related growth he no longer has to worry about what NASDAQ does. He's making fb independent of the media fluctuation or the fact that he has shareholders for all. The question becomes, what would you do if you you had a successful company and you were just given 1.13 bln dollars without any strings?
This is just a thought experiment, but I think fb brilliantly played wall-street and now has enough money to build an infrastructure. Internet advertising isn't creative, so what will the "next gen fb" look like? And is it worth investing in, speculating that it means nothing to them.
He still has much, much more tied up in facebook. The fact that he's diversifying his holdings shouldn't be held against him; any reasonable person would do the same to hedge against a possible decline of the entire technology sector in the event social media company valuations face some sort of "correction". Also, anyone with that much money in equities has to worry about broader macroeconomic issues such as the current problems in Greece and the rest of the Eurozone. Once again, Zuckerberg isn't doing anything that should be held against him. He still has most of his eggs in the facebook basket; he's merely being prudent.
The sort of person that faced with ownership of Facebook would say he would just retire and travel and dabble in philanthropy is also the sort of person who would sell out of a Facebook for $500m a few years earlier, $100m a year or two before that, $50m months before that...
Bill Gates is hardly "dabbling" in philanthropy, though. When you try to eradicate a major disease as the first step of your long-reaching plans, you get to use nicer words than "dabbling".
I wasn't intending to describe Bill Gates (although his fortune is currently $60b which is 60x what Zuckerberg apparently has in the bank and bigger than IIRC his holdings of Facebook), but most billionaires don't seem nearly as serious or careful about their philanthropy as Gates. Take Zuckerberg - he's not off to a good start with just donating millions to schools; that's not going to change anything like Gate's "let's eliminate polio forever" would.
I think we are going to need a new term for legitimate ponzi schemes to help identify them now that anything somebody doesn't agree with: FB, social security, socialized medicine, unions, groupon, quantitative easing, bailouts, unicorns, etc... are now routinely written off as "ponzi schemes".
no kidding. ponzi scheme is pretty easy to define. overvalued stock is not ponzi, it is just an overvalued stock. ponzi is paying earlier "investors" with the money of later "investors". Under that definition, only social security from your list fits even close.
