I am a believer of freedom of expression so I'm also of the opinion on doing away with the infraction function if it's subjected to abuse more than serving it's purpose. But I guess Sam has his reasons and sees it differently. Anway, if too many reports of abuse, I believe he will find a solution to this.
I have a couple of "theory" of why Sam maintained an infraction system like this. All stemming from trying to keep traffic up and being lazy enough that you get others to do the job for you of keeping the forum decent enough.
1) Reward long standing contributors. Notice that its points/reputation base. In general, if you can gather enough reputation you should also have the foresight to try to keep the forum decent. I.E. banning people that are abusive.
2) Infractions encourage people to be more obsessive about gaining "reputation". Hence more post, activity in the forum. Some of the infractions are basic tick for tacks responds. You infract me, I'll infract you back tomorrow etc.
In general, I do not really care if there is an infraction in place or not. As long as my views are heard and shared. It gets abusive on point 2) when people start using the system as some sort of personal vendetta.
I believe there're some trouble makers going around doing mischief just for fun of it.
There is always troublemakers. Most of the time it does not really matter what they say or do. If they make the forum "unreadable" then its a big concern for me. I'll just stop coming in thats all.