There's nothing decent about WiFi that links your customers to the creepiest personal info vacuum on earth.
http://www.zdnet.com/firm-facebooks-shadow-profiles-are-frig...
Nothing stops someone from tagging you in a photo. Nothing will stop people from posting "Hanging with XXX @ YYY". Putting 2 and 2 together: they now know who you are, types of places you visit, and what you look like. And you never made an account. After this your choices are:
- get radical with friends about what they post about you
- give in and use facebook
- stop hanging out with your friends