Warren Buffett and Bill and Melinda Gates met with Charlie Rose this week to talk about The Giving Pledge, in which they are encouraging affluent people to give away half of their net worth in their lifetimes or after.

If they are successful -- and who would bet against those three? -- the impact could be remarkable. For instance, Buffett talks about the fact that $230 million of estate taxes were owed in a recent tax year, of which about 12% were pledged to charity. Boosting that to 50% could have a stunning effect on philanthropy.

This isn't, of course, the first time a challenge like this has been put out there. As we write about in our book, Anne and Christopher Ellinger created Bolder Giving more than a decade ago, with one element of it being the 50% League, a society for those pledging to give away half of their net worth. They have been asking givers to sign a pledge and take on a "challenge."

Our family has always been torn about issuing challenges. Joan and I are a bit reticent to push people, believing we should speak with our actions. Hannah, on the other hand, at every turn challenges others "to just stop, and to think about what you have more than enough of in your life that you could give away." She is firm and direct.

The styles may differ a bit, but the message is the same: Give because you can help. Give because it feels great. Give because the world needs your gifts, financial and otherwise. Just give.

Two things, by the way, about the Gates/Buffett activities:

1. Melinda Gates talks about our family at about the 25-minute mark during the Charlie Rose Show (thank you, Melinda, we are flattered!).

2. Warren Buffett's personal pledge is a remarkable read -- not surprising for a guy whose Berkshire-Hathaway annual report letters are the corporate read of the year.