my 2 eurocents:
Yes, you can be hit and killed by friendly puffy ack. Happened to most of us.
But it's still not as dangerous to you as to the enemy, because the ack doesn't aim at you. Currently, being hit by friendly ack is still a kind of freak accident.
Until now I was fine with that. But what I do now see it indeed as a problem: When we are fighting 30+k over the new strat targets (thats 2-3x higher than most top level action over CVs), the ack as still an uncanny ability to identify targets at that extreme ranges. One sortie I was trying to drag away the enemy escorts from their bombers. When entering the ack zone; I suddenly saw puffs all around them, while myself being totally safe from it because I was 1.5k in front of them.