i might be wrong, but I believe I was talking to XBain about that topic, and I mentioned that
a) the one who didnt show up should be punished
b) the one who 'won' shouldnt get any points
I actually believe he agreed on that and said it will be done this way, so we will have to wait to hear his opinion. I personally think that it's not good that players can get some default wins this way, but that also will be a problem with something else: what if somebody just matches newbs? He might rise in the ladder quickly (up to a certain extent, where he will only get very few points for a win).
Of course, you will be forced to accept challenges of challengees who sit close to you in the ladder... XBain will post up the rules soonish.