Maybe in Gates' case this is true, since he seems to carefully evaluate good causes, but in general it isn't. A lot of the charitable donations that the wealthy use for tax write-offs go to things like museums and universities with already-huge endowments. Not that these aren't important, but it's not exactly Habitat for Humanity or soup kitchens. Frankly I'd rather see that money spent on government social programs.

The more I read about this, the more I come around to the idea that charitable tax deductions should be ended entirely (actually I think all tax deductions should be phased out, but that's a bigger topic). It's effectively just another regressive tax.