There is no such thing as true altruism, and that's a good thing.

Bill Gates pledges to donate 95% of his wealth to charity. This means that the value Bill Gates places on his own self-pride and self-satisfaction is in excess of 95% of his net worth, or just over $80 billion. Let's also recognize for a moment that he could have chosen to do a number of other things with this wealth, such as purchasing a few islands, several yahts, vacation homes, cars, any number of things would benefit absolutly nobody but himself, but for which he would also experience a large amount of self pride and satisfaction by being able to show off all these expensive things.

Now let's consider what Bill Gates would need to do in order to fit the true definition of "Altruistic Behavior". He would essentially need to find a way to sacrifice his wealth but experience absolutly no joy, satisfaction or other kind of intrisic reward in the process. One way to do this would be by dropping stacks of cash into a woodchipper, for which he would experience no reward whatsoever (other than the fun of watching stacks of cash explode into tiny peices) but this act would be stupid, wastefull and pointless.

Performing a truely altruistic act like this has absolutly no meaning, for the exact reason that there is no pride, satisfaction or reward associated with it. The act has no purpose and offers absolutly no net value. Therefore, perhaps we should should be glad that a truely altruistic act does not exist, but also be glad that altruistic people do.