Should also add that such a system is unfair to players who only attend 3-4 games a season, while some players are regulars. Freedom Fighter would easily gather 30 or so points a year, while I may only get 5-8. Minimum 10 point limit for an event? I'm out.
If you're going to record all data, positive and negative, the host has to add the whole list of attended players to the positive column, and any flakers to the negative.
I think that the easiest solution is to require prepayment of the event. It secures you a spot and also gives the organizer some liquid assets to play with before hand. Large events are planned months in advance and give players loads of time to get in their payment. As Dragonhawk said, it's not as critical for smaller weekly games.
As I've said for Operation Pine Ridge, there's a "No Flake" Policy in effect. When you show up, you're there for the whole thing, no matter what. Sorts out the men from the boys. You leave early, you're on the blacklist. The only exception I've made is for Lisa and Katey because of Katey's Dialysis..
"Solving an imaginary world's contrived and over dramatic problems... 6 millimeters at a time."