I was hanging out in the Mission yesterday with a friend and checked-in to Dog Eared Books on Foursquare. I was intrigued to see an ad for a "special nearby": Foursquare told me that if I check-in nearby at Her Majesty's Secret Beekeeper, I would be treated to a free honey stick. We decided to check out the place, and sure enough got to sample some great honey, and have a great chat with the owner Cameo Wood. Cameo is an early adopter of a lot of technology, and had been a beta-tester for Foursquare before she jumped onto their advertising program.
Now, I am not the kind of person who would ever have walked into a honey & beekeeping supplies store. But I really enjoyed this serendipitous experience and am now happy to promote this shop to other friends who might be interested.
Of course, Foursquare's primary value is as a social tool to meet people. But as a side-effect, it also connects people with places that they wouldn't have discovered otherwise. And that makes it a very powerful advertising medium for any local business. I had read about Foursquare for Business before, but it was great experiencing it first hand.