It depends on your location, different countries have very different laws.

For example in most countries it's perfectly acceptable to have someone in a picture that you're taking in public (for example you're taking a picture of a building and someone happens to walk by). A notable exception to this is France, where apparently the right to ones own image is quite strong which technically makes most pictures of the Eiffel Tower illegal (as long as any one person is identifiable on it).

Taking (and distributing) a picture specifically of a specific person that's just doing random stuff in public is already less uniform and varies. There's often some protection to basically say "no, you can't make fun of some random person for having the wrong tshirt, they have a right to privacy". A notable exception to that is usually "public figures" (which mostly means people in political, religious or commercial leadership positions): they mostly just have to accept to be pictured wherever.

Protection for pictures taken in a private is usually the strongest (so yes, if you post a picture of your 3 best friends at a small party in your home, you might have to ask them for permission!)

How all of this applies to pictures that "aren't real" but look disturbingly so is probably going to be fought over in court for a good while.

No, human right. And yeah, they mostly are. But it's not Facebook offending but each of the teens, so nobody can really enforce it. Same like with phone numbers, except that those are actually protected by law in most countries.