Never should happen unless you are in danger. If a woman posted that a man would hit her in the groin it would be considered to be abusive and assault. Same should be if a woman nails a man without reason. If you are not in danger, there is not an excuse for causing that kind of pain on a person.
That area can actually be kind of hard to hit at the eat of the moment so as far as self defense goes don't make it your only technique. For all you know he could be wearing a cup anyway. If you do manage to hit the guy there, having experience getting hit in the balls it hurts alot, like 3 times as much as if you had been sucker punched the stomache without tensing up. The pain is lingering, flowing though you while making making you sick to the stocmach
self defence classes tell you not to kick there because it is one of the first places they expect you to go for. the knee and the eye gouge is what i hear lot, also a hard fast downward kick / slam into the shin...especially if you have heels on. or keys between your fingers and aim for the eyes. but definitely take a self defence course and if possible talk to someone on a cell phone as you walk. my girlriend used to call me when she had to walk around at night -anytime- at least then i'd have an idea of where she was and possibly a description who it was if something did happen.
In self defence we were taught to knee in the groin or do gst - grab, squeeze, twist if face on, or to elbow slam if grabbed from behind. Also, we were told to jab the eyes and, if possible try and scrape some dna out of the nose or pull some hair out. and yeah, cellphones and screaming are also great ideas