Dude, if someone hugged me from behind, I'd probably end up elbowing them in the face out of surprise. :p

Hugging: no
Grinding: self control is the way to go

If a girl is 'grinding' on you and due to your amazing 'self control' she doesn't feel something happening, she will probably think you are impotent.

Very nearly happened to me Friday

define hug... when me and my neighbor are half drunk and spend an hour before we fall asleep "hugging" and just laying on eachother then usually, but if im just hugging my gf in school or something then no until she gropes me

Aww that would be sooo awkward! Never had it happen to me =/

Hasn't happened to me since middle school...don't worry about it