Its a great feature, well done
Though I do have a bug report to make....
Members of groups who don't have permission to play this game are reporting getting the "hit by a snowball" PMs. This is because the members who do have permission to play are able to access the tab for this game on non-player profiles, and throwing the snowballs at them... even though there is not permission to do so the other way round.
If a usergroup doesn't have permission to play this game, then they shouldn't get any notifications related to it at all, and it would probably be better if the tab wasn't available on their profile at all either - even to those who do.
Cheers