My team's pointed out that I didn't actually say what we built. TripAdvisor runs the Cities I've Visited Facebook app: http://apps.facebook.com/tripadvisortrav

My team's pointed out that I didn't actually say what we built. TripAdvisor runs the Cities I've Visited Facebook app: http://apps.facebook.com/tripadvisortravelmap http://apps.facebook.com/tripadvisortravelmap Over the last 3 years, we've collected over a billion "pins" worth of data across millions of users. Our MAU is about 5m. We've added Facebook Connect to our site and now have a box on each geo-specific page on our site which shows you which of your friends know about that location, based on their data in our pin database. What this means is that we find the short list of friends that can actually help and influence your travel decisions. The tools also pulls together responses from email & wall posts so that they don't disappear into the Facebook limbo. The part that I think is awesome is that we got to build something truly valuable and useful based on data gathered from a compelling and popular Facebook app. See it yourself: http://www.tripadvisor.com/cambridge,ma http://www.tripadvisor.com/cambridge,ma