Honestly, even if people did "behave themselves" and only add or vote for properly named and appropriately old enough games, it wouldn't matter. The wishlist in its current form is not user friendly at all, since it doesn't allow for any sorting and really can only be searched. Until GOG updates the functionality of the wishlist (possibly as a part of Site Update 2), it will remain a barely functional component of the site, no matter what we do.
The only wishlist items we should really have a problem with people adding or voting for are the duplicates of existing games and games that are obviously bullshit. The fact that new games are on it is not a problem at all, since it is a wishlist, by definition it should have things we could only wish for on it.

I had a muffin for breakfast.