Location based services are the new poster child of digital marketing. Facebook is rushing to add the functionality to their site in response to hot start-ups such as foursquare rolling out. But is it worth the average business getting involved? An interesting article on Masahable (click here to read in full) would lead you to think perhaps not due to the poor uptake on the service at the moment. Only 4% of the adult, Internet using population has used any kind of location-based service, and just 1% of all adults check into a location at least once a week.
By contrast, more than 11% of online adults have used Twitter, and an estimated 28% of all Internet users have signed up for Facebook (Facebook).
So my advice would be to focus on facebook & twitter at present, but keep an eye on sites such as foursquare as they grow in user-mass.