The thing is most players do not care when others get their head. Heads given to a killer is meant to be a "trophy", similar to how Diablo 2 has ears. There is an option coming for it tonight ,but it will be default on, but super simple to turn it off on all servers. Though RIGHT NOW, Player head drop was reverted to original behavior of only going to your own inventory. So you can PvP safely right now without worry about your head. But I want to default it on because for most people they won't mind, and it adds a fun element to the PvP of getting trophies. I also would not be shocked if Mojang even made this default behavior for PvP kills.
