Recently I heard as a general rule of thumb that one should leave at most the width of your hand as space between the knot (a figure eight for instance) and the harness. Its quite obvious that one doesn't want one or two feet of rope between the harness and the knot, since it might catch on something, but I never paid too much attention on whether its one, two or three times the width of my hand.

Aside from it being caught on something, are there any other dangers associated with having too much space between the knot and the harness?