NOT discussing the moral implications here, but I saw this study and found it relevant. One of the arguments re: PUA is that there have been no scientific studies as to whether it works or not. Apparently, that isnt true. Here is a link to an article about a study that shows that a light non-sexual touch (what the PUA folks would call "kino") ups the chances that a woman will give you her phone number.

The relevant part is #7 "Touch for a Date". Excerpt:

Perhaps more surprisingly women also responded well to a light touch on the arm when being asked for their phone number by a man in the street (Gueguen, 2007). This may be because women associated a light 1 or 2-second touch with greater dominance. (Bear in mind, though, that this research was in France again!)

I can't access the full text of the actual study, but maybe some of the university students here can read and summarize.