If you see a friend or a loved one performing these actions, please notify the authorities immediately.

This is big pet peeve of mine, because I see even experienced artists still not able to draw a bra or bikini top in proper perspective.

Instead of using the cleavage as a guideline (a common mistake), I suggest using the nipple as a good way to establish symmetry in perspective.
This is less of an issue with smaller chests because their plane is closer to the front surface of the torso, but larger breasts often fall victim to these sorts of oversights.