In general, I don't mind people I know touching my hair. Most people will pick up and play with one curl, which is fine.
What I don't like is strangers touching my hair, no matter how they touch it. I just think it's weird, especially when they don't even preface the touch with a comment. They just silently touch it and don't even say anything when I look at them. Very strange. I mean, I'm intrigued by certain things about people too, but I would never think to touch someone.