Consider two situations:
1) Zuckerberg wants to preserve his fortune whilst gaining good PR for donating money to charity.
2) Zuckerberg genuinely wants to change the world.
In (1), it clearly hasn't worked then given all of the comments around here. Is it not highly likely that he would have considered this backlash that he received? If I was in his position and wanted to achieve (1), I would make a high profile donation of ~$1 billion (~2% of his worth) to a respectable charity.
The global distribution of anti-malarial bed nets would never have as great an impact on health and poverty as something like the invention of the electric light bulb. Sometimes what is best for increasing quality of life around the world isn't the redistribution of wealth and cannot be achieved in a charitable structure. In scenario (2), it is completely reasonable to set up an LLC for this purpose. Instead of thinking 'what's the worst he can do?' think 'what's the best he can do?'