I use Wishlist to keep interest in games and don't want some of my friends thinking I equally want each game if they decide to gift me games. However if I want to private my Wishlist I also private my achievements, owned games, playtime, and play status. This feature should be made further toggleable, at least in regard to Wishlist, but ideally playtime and "in-game" status too.
Alternatively wish listing itself could have an option to keep certain games public, open to friends, or completely private.