If I'm comfortable with you and we're quite close then I don't mind too much. It still makes me feel uncomfortable at times. But if I'm not acquainted or friends with you then I'll probably just freak out because I absolutely hate being touched. :c
It depends on the person, say, if it's a girl who I find attractive, then sure, do whatever you like, haha. I do hug my friends or get close though. Even the guy friends aren't afraid to grab you from behind and pretend to rape you.. We're not actually homosexual, we just like to mess around.
If it's gross little kid I really don't like them touching me, every afternoon I'm on a bus full of them, and they are not the 'cute sweet naww' kind, they are rats, the entire bus trip home is a loud, non-stop screaming and swearing and hitting and rude little bastards haha. This bus is completely packed, and even the isle is packed, and the little kids always try and push through and it's so annoying, and very awkward because they sometimes... Touch things...
But yeah, most of the time, I'm pretty comfortable in touching, and most of my friends, if you accidentally touch something, we just laugh and wink. (But that isn't permission to try anything)
I don't really mind physical contact. With friends, I'm quite an affectionate person and that translates into physical contact (like hugging, kissing on the cheek, etc). I use it mostly as a way of showing people that I am comfortable being around them. Though if I'm drunk, that extends to most other drunk people, haha.
However, there's a difference between being friendly and being inappropriate and I'm fine with the former but not the latter.