I had some friends that did this last year and it seems like they were always doing some sort of fundraiser for it. I was always getting emails about bunco nights, etc. I guess they enjoyed it, but have decided not to do it again.
My advice would be to look into how Komen distributes the money and what they do with it before putting in the time and effort. If they seem worthy to you, then go for it. Personally, I put my time and effort into lesser known charities and diseases because need the help so much more.