I like the 'only-negative' feedback option, and i'd like to suggestion something similar.. or an 'upgrade' if you will.
An only-negative feedback, which is hidden from everyone, up until the point where there are say, 3 negative feedbacks entered to that name. Then, the negative feedback icon would appear under the player's name (just like the Trader Rating).
This would help with the 'miscommunication' and the 'last minute hospital call'.
As a side note, i'd also like to mention the LIFT problem. Its happened to a lot of players, where they all confirm, but the driver cancels... ultimatly, 4 players do not show up even tho they were all confirmed... And its not their fault... If a system is instored, it should account for that.
Perharps a good way to do this would be to have only the organisators who actually 'Post' games in the 'games' section be able to leave ratings. It would then be their responsability to take presences at their games and later on, leave negative feedbacks on anyone who didn't show up if so desired?