Some bloggers and internet marketers swear by it. I’ve heard it over and over that “you need to increase your keyword density” or “don’t go too high or it will considered spammy”. The idea just makes sense doesn’t it?
I must admit on the surface without any careful consideration the thought of an ideal density makes sense. However this is just not the case. KD tools are not useless altogether. They might inform you that you haven’t used your keyword at all or you might be overdoing it.
Outside of that there is no real value in the measurement.