A recent story in Fast Company explores the effect that location-based social media sites like Foursquare, Facebook Places, Groupon, and others have on driving consumers to buy. Apparently, so far it's not much.

The article focuses around Applied Predictive Technologies (APT), a data and analytics company that works with some of the largest retailers and restaurants in the world. The company measures the incremental impact from traditional and social media campaigns on sales - similar to an FDA trial for marketing.

Based on the data provided to the magazine, location-based social sites have had a minimal impact on sales. While there may be a small bump in sales from a successful promotion, the company finds that these increases are temporary and geared to special deals, etc.

Until these campaigns can deliver sustainable increases in business, APT doesn't believe that there is enough reach to be able to drive the level of change that one could drive with a successful capital investment.

But marketers should not give up hope. APT's senior VP believes that this is a nascent industry, and that maybe they just haven't figured it out yet.