Prey:
2
a : an animal taken by a predator as food
b : one that is helpless or unable to resist attack : victim <was prey to his own appetites>
In this case, the prey are unsuspecting teenage girls who are powerless to prevent horny men from prowling their Facebook profiles for photos to circulate into underage spank banks (or for personal use).
Can you explain what you mean by "predatory"? I understand that it gives you the heeby jeebies. But what predation is taking place?