If you share where you are on Facebook, some merchants will give you freebies of some sort or another. My hair salon does this. If I "check in" with FB, then I get a free little bottle of shampoo or something.
No thanks. My privacy is worth more than some dinky bottle of shampoo.
No, that's not sound right.
You see... Foursquare is the tool of network social. People choice to volunteer to be part of advertising. Where they check in, spread to people to know what's good about this place. It would be good opportunity for local to increase a better business.
However, it's just unfortunately that certainly people being misled and use to check-in their home or any other to abuse. For privacy issues, you can always turn HIDE yourself that nobody will know where you check-in and get discount, receive freebie, or prize. That's what it is for. If you decide not to, you miss the great chance.
I'm one of Superuser Level 1 for Foursquare. I'm part of responsible to correct the details where the local is pin at, include the report if something is misled.
So far, I have been influence to many of friends or strangers who wish to be friends with me. They start to find most interesting and want to go to something different restaurants I have been talk about. I have also spread it from Foursquare to Twitter/Facebook.
It's also good for your own business to spread, too. It cost NOTHING.