At Bicon in the UK, the code of conduct requires that people ask before touching. People hug a lot there, but they nearly always ask (unless they know each other well). It doesn't seem at all creepy because it's a community norm.

I think it's generally an excellent system. Once you've asked a lot of people an occasional no* doesn't hurt. And generally, people haven't seemed offended when I've said no to them.

*It's important to remember that no doesn't necessarily mean "go away you creep." Some people don't enjoy hugs.