10 meters is the longest I use, and for the most part I don't use more than 6 meter cables at all. I don't think that most people really have components seperated by a great enough distance to really warrant a 20m cable. The only use I have for any of my 10m cables, three, is to be wired into the wall, and even then 10m is plenty. Considering how most cables people are not going to bother putting through walls even, 3-6m is enough, I think, for the majority of consumers.