I can think of several reasons why MacDonald made his choice.
I guess you can look at it that way as well. It's just that if I had that kind of money (even half of it) I would be interested to see how it's used. I wouldn't donate it to rather anonymous charities anyway. I'd be more likely to set up my own fund and distribute money to projects I find most worthy. Similar to what Bill Gates is doing only on a more modest scale. He seems to favour treatment of rare diseases, I'd probably favour education but the idea is similar. For me that would be the most fun part of having really huge amounts of money! Otherwise if you are just sitting in your corner and watching your numbers grow already far beyond any likely personal consumption it seems like a waste. Just my opinion of course :)
Buffett used to believe that he could compound his assets during his life to result in a far larger bequest than any charity could manage on their own. (He's been on the boards of university foundations, so he would know.) He figured that giving it all away would be Susie's problem. Then she died and he was planning to dump the same problem on his kids, but then he had the pivotal discussions with Bill Gates.
Buffett still believes that he can grow the money faster than Gates could manage it, so he's compromised by spreading the bequest out over a 20-year period. He also doesn't want to end up creating a perpetual charity like the Ford or Rockefeller foundations, so he's required the Gates Foundation to cash out his donated shares every year and to spend it all within a certain time period (which I believe is 20 years after his death).
One of the things that annoys me about some charities is that, once I donate, they continue to solicit me for donations at an alarming frequency. Often I end up feeling like every dime I donated in the first place gets spent mailing me stuff to try to get me to give them more (although it has the opposite effect in my case.) I don't want to be called, sent "informational emails," or to receive magazines, return address labels, and the like. I also don't want people pandering to me and trying to butter me up to get more donations, and this is what happens as a follow up to particularly large donations. Perhaps that factored into his decision to just keep it quiet and give a giant chunk at the end?
Well, he could've opted for a charitable gift fund. That's the answer for the rest of us, unless we use our own funds to buy tickets to a charity event.
MacDonald could have tried a second option: Charles Feeney co-founded the company that became Duty Free Shops. When he first started giving away his money, he included a confidentiality clause that forbid the beneficiary from even acknowledging the name of the charity (let alone Feeney). He gave away hundreds of millions before his philanthropy became public knowledge, so it can be done:
http://www.forbes.com/sites/stevenbertoni/2012/09/18/chuck-feeney-the-billionaire-who-is-trying-to-go-broke/MacDonald was probably just more like Buffett than Feeney.
Third possibility: my spouse served with an officer who was gung-ho Navy blue and going for admiral... until her parents passed away. The parents' will established a charitable foundation from their estate and placed her in charge of administering the millions of dollars in assets. As soon as she realized that she was entitled to a reasonable salary for her duties, she filed the military's fastest retirement request. Her attitude and her priorities changed so quickly that her CO called BUPERS and said "Get her outta here--
now". Instead of the typical 6-12 months, BUPERS made it happen within 60 days.
So maybe MacDonald was trying to give someone lifetime employment.