Protect an Ally Ping

If you can ping an enemy champion for your team to focus on, then why not allow us to ping our ally champions so we know who to protect before a fight begins or some other circumstances. I think this would sorta but not really deal with the flaming in chat so people don't start complaining. This also might be good for that one person who sees's that an ally is being attacked by the enemy and no one else is paying attention.