He's suing for loss of fun and games.

I'm guessing this doesn't really get anywhere ... even if he wins the suit, the reward will be fairly small, it will be appealed and 12 years from now he'll get $30,000. But if he does win big then one result will be a lot more netting around the park. I'm somewhat surprised they haven't done more of this already.

So legal beagles -- does the existence of netting for part of the park show that (a) teams recognize they have some responsibility to protect the fans (i.e. liability) and (b) they can't argue this sort of injury was unforeseeable?

They won't argue unforseeability since the "baseball defense" is essentially that the risk is well-known by the plaintiff and he assumed that risk in attending a baseball game.