Proof of Dining

Proof of Dining is almost entirely about geography: Reviews reference restaurants, and PostGIS does the rest when a user searches for places nearby. The reviews themselves are a stark contrast to those of other sites: A reviewer must provide a photograph of what they ate (the "Proof of Dining"), and every review is manually checked and approved. No shenanigans.
Proof of Dining

PostGIS is used extensively throughout the app, providing the infrastructure for performing fast geography-based searches and a means to relocate misplaced restaurants. Each region (whether a zip code or city-state pair) has both a centroid and boundary defined, which are used to center searches and aid users in finding nearby restaurants and reviews.

Game theory is also employed in the app: Reviewers gain points for various activities like performing reviews and engaging in socializing (like the invitation system). The points, in turn, can be used to claim coupons from restaurants (though some coupons have no such requirements). This "achievement system" is represented by badges on a user's home page.

Both restaurants and advertisers have a gateway into the app to manage their data. For restaurants, that means their menu, photograph, and other details. They can also respond to reviews about their meals. Advertisers can choose different types of campaigns (local, regional, or national) with placement on different page classes (home, search, and standard).