As an ISFp I don't usually go out of my way to touch others, but I normally don't mind if they touch me just as long as I know them well enough and I'm comfortable with them. I have an INFp friend who will do EXACTLY what maizemedley described doing with her ISFp friend.

As for a function that keeps people from wanting to touch others, I don't know. I know that I would hesitate depending on the person. There are some people I get the feeling that just don't like to be touched so I avoid touching them.

The ENTp I know HATES to be touched, especially by males and most females. He seriously gets hostile about it. I also know an INTp who doesn't like it when other people touch him, but he's not completely averse to touch, if it's on his terms he doesn't seem to mind it so much.

I know an ESFp, INFp (the one I mentioned above), and ENFp (all females) who are touchy feely. Especially the ESFp and INFp.