Andersp:  I disagree.  As I stated earlier, backgammon is a skill game with a random component.  A rating system is appropriate in backgammon to measure the players' relative skill.  It just takes more games to establish a reliable indicator of skill because of the random factor.  There are rating systems that work very well on other sites, mostly based the granddaddy of them all, FIBS.  This is not to say the rating system here doesn't work, but it does have serious defects.  The problems pointed out by nabla and Abigailll are the most significant ones.