Herve,
I definitely see your point, and it does make me think.  I think there are often unexpected and maybe even delightful benefits to being kind.  Perhaps these results do make us want to do more kind things, even if nothing comes of them, they are not "cost effective" and we are not even a "star."  I hope we can at least direct our efforts knowing they do not always have to result in short or long term benefits to us.  Is it enough just to be kind?

On another note, I wonder what you think about how we actually work to increase acts of kindness.  Why do some people act in this way without thought while it never occurs to others?