Bryan Caplan doubles down on the voluntary taxes talking point:
All genuinely charitable donations suffer from the Prisoners' Dilemma problem that Will describes. That's probably a big part of the reason why charity is only a few percent of GDP. But none of this explains why out of the more $300 billion that Americans give to charity, the American government garners about $3 million. Despite widespread nationalist and statist sentiments, Uncle Sam's share of the charity market is microscopic – less than .001%. How very odd.
Jonathan Bernstein pushes back:
Suppose that Buffett believes that $1000 … would create $1500 in benefits if it was given to charities he selected; $1200 in benefits if it was given to government; and $800 in benefits if it was given to the charities everyone would actually choose (because in practice a ton of people are going to give to scams, or to charities which he believes do more harm than good). So if it's just his $1000, he'll give it to the charity he supports (over government) — while still preferring a system in which he's constrained to pay that $1000 in taxes as long as everyone else is. In other words, he'll accept using his own money sub-optimally (in his own view) if it will buy everyone else contributing.
The Dish 