Deductions for charitable contributes are capped. There is also the difference between what Bill Gate's paper worth is and what his tax liabilities are for the year.
Not for capital gains if you sell the underlying asset. If I buy a stock for 1 cent and donate it then I avoid all capital gains even if it's now worth 30 billion. Considering the original baseline Gates working with it's ~30 billion * .15 ~= 4.5 billion tax savings. You also get to deduct the original 1 cent from your income, but as I said your avoiding the 50% income cap on donations.
I agree that his paper worth and taxes are separate issues, I am simply stating that having a charity sell stock is much better than having a person sell stock for the amounts involved. And it would be reasonable to charge capital gains at the time of donation for the same reason it's reasonable to remove the donation tax break. To further prove the point if your dealing with a deprecated stock it's better to sell and then donate.
