Take a look at our API directory and you will quickly note that the Google Maps API continues to reign as the most popular API used for mashups. As the API continues to gain momentum, several new utilities have emerged to improve the user experience (or UX as it has come to be known).
Location-sharing service Foursquare was down most of Monday, apparently due to a database issue. No Foursquare website or apps were available. And with the API also down, third party applications were helpless. Yet, it's a good reminder to developers to plan for downtime and to providers to have communications in place to let others know about your service's issues when they arise.