Foursquare is a relatively new social networking "game" based on exploring your city. More importantly, it's now a marketing avenue for businesses.
At the core of all sales and marketing success is a strong relationship with your customer. You create trust, loyalty and expectation because of quality and consistency. However, sales and marketing are often approached with an ROI mindset, with no emphasis on customer lifetime value.
Sales is a numbers game. You will never find a salesperson that bats a thousand (in leads:closed business) because there are simply too many uncontrollable client variables. The best way to "Always Be Closing" is to populate your pipeline with enough strong leads to combat the likelihood that nothing will close.